WO2016099268A1

WO2016099268A1 - Method for inspecting the treatment of food products

Info

Publication number: WO2016099268A1
Application number: PCT/NL2015/050874
Authority: WO
Inventors: Gerrit Jan DOORNENBAL; Leonardus Paulus Crezee; Eddy Alfred Herre Van Der Goot; Rudolf Johan VEENEMAN
Original assignee: Moba Group B.V.
Priority date: 2014-12-19
Filing date: 2015-12-17
Publication date: 2016-06-23

Abstract

The present invention provides a method and a system for inspecting treatment of an organic or inorganic material piece of for example a food product or of a package unit, more particularly of a predetermined part thereof, whereby for example information is applied or removed, wherein the method comprises optically inspecting with at least a single camera. More particularly, images are made, at standstill of the material piece near the treatment unit, prior to treatment and following treatment, whereafter these images are compared with each other, differences are established, and on the basis thereof it is decided whether the treatment has succeeded. In a highly suitable manner a fast and widely applicable methodology is obtained for inspecting treated food products, for example the provision of prints thereon or also the removal of dirt therefrom, or also the provision of prints on package units.

Description

Title: Method for inspecting the treatment of food products

The present invention relates to a method for inspecting treatment of an organic or inorganic material piece of for example a food product or of a package unit, more particularly of a predetermined part thereof, whereby, for example, information is apphed or removed,

wherein the method, for example but not exclusively, comprises:

- inspecting of the printing of for example information or of a figure whereby a printing unit as treatment unit moves along a printing path over the material piece and applies thereto the information or figure whereby a print is obtained; or

- inspecting of the cleaning, with a cleaning system as treatment unit, for example for washing or brushing, of food products such as for example eggs, fruit, or vegetables, whereby dirt is removed;

wherein the material piece is stepwise conveyed along a transport path on a conveyor, for example belt conveyor, moving in a transport direction T, wherein the method furthermore, for each successive material piece, successively comprises,

- at standstill of the material piece near the treatment unit:

- choosing as image field the above-mentioned part of the material piece that is intended for treatment, for example printing or cleaning,

- making, with at least a single camera, a first image of the above- mentioned part prior to treatment, this first image or the before- image being composed of pixels, and whereby for each pixel first image signal values are obtained,

- treating the material piece, and - making a second image or after-image of the image field after completion of the treatment, whereby second image signal values are obtained, and

- thereupon comparing the first image signal values with the second image signal values whereby for each pixel of the images difference values are obtained (for example, intensity difference values).

Furthermore, this invention relates to a system for inspecting treatment of such products, such as, for example but not exclusively, inspecting the printing of information or figures on food products or package units of food products, or the cleaning of food products such as eggs.

In the world of food technology, increasingly higher standards are imposed in respect of what is called food safety. This is understood to mean, for one thing, that origin and composition of food products should be available to a purchaser in a clear manner. In contrast with bulk materials such as powders and liquids, for example meal, oils, juices, etc., which are packed in sealed packages, provided with advertising and quite commonly configured after well thought-out design, the labeling and coding of bulk products and harvest products such as, e.g., fruit, vegetables, and eggs, is considerably more complicated, not only because of the packing and the labeling of either the products themselves or the package, but also because the origin and harvest date or packaging date of such products in most cases are less easy to specify accurately. Moreover, labeling of such harvest products, to be considered as natural products, presents technical problems because of the regularly varying shape and the quite diverse situations for adhesion or application.

While in the past such products were treated and traded manually, nowadays this involves the, mechanical and automated, harvesting, collecting, storing and preserving, and then sorting and packaging, of huge quantities of such products. In such a handling process, practically every manual contribution has been replaced with automated handling.

In the case of eggs, for example, machine capacities of about 200,000 eggs per hour are involved.

Another example in the world of food technology concerns the cleaning of food products, such as vegetables or fruit, and also, for example, the washing of eggs. Inspecting such a treatment is very labor-intensive.

From EP 1032831 it is known to detect dirt on eggs which are, for instance, supplied as a stream of products on a sorting machine. Based on such detection, a selection can be carried out for removal from the stream.

In EP 1094700 a conveyor system for eggs is described in which via a specific system of carrier rollers the possibility is reahzed for each egg, upon a detection as mentioned above, to be removed individually from the stream. According to EP 1469719 an adaptation of a conveyor system for a stream of eggs with washer coupled thereto is described in which an extent of fouling common in this field of technology is taken into account. An essential link in this adaptation is a detector for detecting eggs not duly cleaned which can be taken from the stream immediately after the washer and, if necessary, be placed back for rewash.

For the drying of eggs, reference is made to, for example, US6357140.

In the above cases, once-only, images or scans are made in which by means of image recognition procedures, introduced into the detector as software or by teaching-in, eggs are labeled and accordingly selected.

In the present disclosure, a treatment as mentioned concerns, for example, the printing of organic material pieces, for instance surface parts of a shell of an egg, the printing of a fruit or vegetable product (apples, melons, tomatoes, peppers and/or the like), and/or the printing of other organic product parts. More particularly, hereinafter an exemplary embodiment is described in which package units (mostly inorganic material) for shell eggs are printed with an ink jet printer. Such package units mostly have the well-known division of 2x3, 2x6, etc., nests, with an egg received in each nest, while these nests, as well as a lid foldable along a crease, are formed from the same piece of material, typically pulp material.

In the field of sorting eggs and then packing them in such package units, it is especially these lids of pulp that are printed with information and/or figures typically comprising all kinds of origin information. After printing, the package units are mostly grouped to form layers of patterns of them and then palletized. Examples of, on the one hand, the filling of such package units, and, on the other, the grouping and stacking of such package units, are described in US5232080 and in WO2007133079, respectively.

As explained above, it is expected and required that complete and detailed information about origin and transport of such products, here eggs in particular, be clearly represented on a package and such information be properly legible and thus the products be traceable.

For this purpose, suitably, use is made of, for example, ink jet printers. Such a printer is described, for example, in US6332677. It is generally known that their functioning is most closely connected with pollution of the minuscule jet nozzles and the amount of ink in a reservoir. Especially for the last condition, control is so designed that replacement of a cartridge is already indicated when actually ink is still found to be present in the cartridge reservoir. For users, this is disadvantageous from the viewpoint of business economics.

In the case of cleaning, of e.g. eggs, vegetables or fruit, cleaning can involve, e.g., a combination of brushing, washing and drying, as already indicated hereinabove. In the description and explanations hereinafter, the following measures are mentioned:

- printing,

- the print that is thereby obtained, and

- inspecting of the location where the print has been applied, or where the treatment of, e.g., cleaning has taken place, prior to and following treatment (e.g., printing or cleaning).

In further clarification and in addition to the above, the following holds for the present disclosure,

- that printing is understood to mean at least one or more of: printing, imprinting, providing, or applying, a figure, or an image, or information, and that in that sense also reference can be made to the printing of an object;

- that a print is understood to mean at least one or more of: the physical result of printing, that is, the image, the figure, imprint, or the print, which is provided on, for example, a package unit;

for this notion, in the field of vision technology, the word 'picture' is sometimes used; and

- that inspecting is understood to mean at least one or more of: the making of an image or a scan, or an image of the treated location, for example the location of a print as mentioned, while for the further digital processing and manipulation of the pixels (this word deriving from 'picture elements') for example the CCD or CMOS technology, generally known to those skilled in the art, is applied; the associated image handling technology is called image processing, whereby normally digital images are obtained.

Where in the present disclosure reference is made to cleaning, this is understood to mean, for instance, one or more treatments which may be combinations of brushing, washing, and drying. Accordingly, a treatment unit (to carry out a cleaning as mentioned) can be a brush, a washer, or a fan, or a combination thereof, all in implementations that are well known to those skilled in the art. The image processing applied in such cleaning is, for instance, the same as already mentioned above. In the processes as outlined above, for the package units mentioned, i.e., the egg cartons with nest patterns 2x3, 2x6, etc., transport conditions are utilized of, for example, values around averages, such as standstill of 0.5 s, and conveyance on a belt conveyor with carriers for 1.0 s over a distance of 35 cm. To that end, printer heads for ink jet printing of such a data flow have been so arranged that, upon the above standstill, they will move, and print, across the lid of such a carton in the direction transverse to the transport direction of the conveyor belt, i.e., in the longitudinal '3-direction' or '6 -direction' of such cartons. Thus, a throughput speed for such cartons is obtained of on average 40/minute.

In many cases, such cartons possess an earlier imprint, for example a designation of and information on the type of egg that is packed in these units, for example, so-called free-range eggs, or barn-laid eggs. These designations are to be taken into account in an ensuing printing operation. Hereinafter such earlier print will be referred to as an optical marking which will be used as reference element in an image made by a camera.

To those skilled in the art it will be clear that during the processing of such package units fouling of these package units will occur with some regularity. Not only is the pulp material used susceptible to, e.g., feathers clinging to it, but also, inevitably, in some instance during the daily processing of millions of eggs, fluid, viz., combinations of egg white and egg yolk, being the contents of an egg, will come out and foul the package units, in particular their lids, which is precisely where the print is generally applied. In all these conditions and situations it will regularly happen that prints on package units or on food products such as, for example, eggs or fruits, are incomplete, or even lacking altogether. As possible causes of this, for example the following are to be considered:

- printer head nozzles becoming clogged by dirt,

- a print or parts thereof failing to materialize because dirt covers the printing location,

- a print or parts thereof failing to materialize because cartridge reservoirs are running out of ink, or

- combinations of the three above conditions.

To follow (or monitor) and inspect (or test, or check) the result of printing, in a known manner use is made of cameras, in particular CCD cameras. A widely applied method is that of making a so-called before-image prior to printing, then making an after-image after printing, and finally comparing these images, that is, 'subtracting' these images one from the other, also called the subtraction method, which compares pixel signal values with each other in a known manner.

In the case of a camera and images in gray values, with each pixel or picture element being taken into account, this methodology will give either a resultant image of the remainder in black against a white background or a resultant image of the remainder in white against a black background. According to another methodology, where the color values per pixel are applied, resultant images in each of the colors used (mostly red - green - blue) are obtained. In all these cases, the thus obtained images will constitute an indication of, for example, the partial or complete absence of an imprint.

As already mentioned above, in this quite extensive field of technology, besides many other types CCD and CMOS cameras are used, whereby for images both in color and monochrome, many processing methods can be applied.

It has furthermore been found that in the printing of information or a figure on such a package unit, that is, for example, but clearly not limited to this example, an egg carton positioned transversely on a belt conveyor, which involves displacements both of the printer and of the package unit, that is, during printing and between two printing operations, respectively, small displacements of these devices can lead to misprints or also 'missed' imprints. This has to be taken into account in the image processing referred to.

Referring to all foregoing explanation, so-called misses are caused, both on food products and on package units for these food products,

either by missed imprints as an unwanted consequence of the above- mentioned conditions, viz., those of dirt being present or the lack of ink, or by the movements referred to that can lead to prints in wrong locations, such as, for example, a wrong location relative to the optical marking already present. Unlike in the case of printing, in the case of a cleaning treatment a comparison of before-images and after-images only needs to establish whether the food product has been cleaned and meets the requirements set for the purpose. The image processing discussed above can be applied in the same way.

Examples of vision data processing are described as such in JP2001175854 and in WO2008098284. In JP2001175854 a method is proposed for inspecting, for example, goods printed during transport on a conveyor. A subtraction method is mentioned whereby the obtained print is compared with a so-called master image, that is, a comparison is made with a fixed, set reference image, whereby parts possibly missed during printing are detected. The system used is an assembly of well-known units such as inter alia a CCD camera, a central processing unit with storage medium and suitable computing capacity, and possibly provided with special lighting to determine shadow effects. In the print, details concerning company name, brand, supplier, sales address, etc., may be included. Missed parts of the print are thereupon highlighted, for example by a difference in color. The outcome of this inspection can be represented in a print as white or black. In WO2008098284 a method is described with which edges of picture elements or pixels of an image can be determined, whereby in particular in successive parts of an image, these parts being in the form of a square of, for example, n² pixels with n = 3, the intensities of such pixels are determined and whereby sharp changes in these intensities between the successive parts mentioned signify edges of an image part. More particularly, these images are a representation of measurements of Doppler sound signals of blood flows in the brain.

The object of the present invention is to provide an improved method and improved system for inspecting treatment of an organic or inorganic material piece of, for example, a food product or of a package unit.

In order to be able to establish the above-mentioned misses, and more particularly to be able to establish the presence or the absence of such a print, or whether a food product has been cleaned or not, the method according to the present invention is characterized in that

the method furthermore comprises inspecting the treated material piece whereby the intensity difference values mentioned are established for the pixels of the images mentioned, whereby a well-defined combination of these difference values is taken as a selection criterion for the decision about the complete or partial presence, or absence, of the treatment of the material piece.

With great advantage, the misses are established so that these can thereupon be taken out of the stream of products (e.g., eggs or fruits) or package units (e.g., egg cartons) and possibly can thereupon be provided with a print again.

Thus, in a highly suitable manner, a fast and widely applicable methodology is obtained for inspecting treated food products, for instance, the provision of prints thereon or also the removal of dirt therefrom, or also the provision of prints on package units.

According to a further elaboration, the (intensity) difference values mentioned may concern, for example, bare images (e.g., images concerning an object or product that has not been treated yet, i.e., has not yet been provided with a print/auxiliary picture or cleaning). In addition, the difference values mentioned may concern, for example, images concerning an object or product that has been treated, for instance a product provided with edges of a print/auxiliary picture as mentioned.

According to a further elaboration, a combination of several difference factors is used to classify a difference found, for instance as being an imprint.

According to a preferred embodiment, for example, a combination of difference factors is applied, for example, a combination of at least two and preferably three or more difference factors, to make the decision about the complete or partial presence, or absence, of a treatment of the material piece mentioned. In a non-limiting example of the invention, the following three factors are applied:

• The difference between before-image and after-image is greater than a defined limit

• The pixel is in the neighborhood of an edge pixel (because letters have many edges)

• The pixel has a low intensity value (is hence black) (because they use black ink)

The combination of these three factors then determines the decision whether the difference found is classified as being an imprint.

It has been found that when the method according to the invention is applied, in printing, a suitable method has been obtained of spotting pollution and dysfunction of the printer head. Early spotting of such failure of a printer head prevents possible aftercare of the multitude of package units that have incurred a miss, thereby limiting economic losses for instance entailed in the interruption and halt of the production flow for shorter or longer periods for clean-up or also for replacing parts.

It is noted that according to the invention the above-mentioned use of a master image is specifically not applied. Since a master image during image processing functions as reference and standard, especially in comparing huge numbers of images, that's where the benefit of a master image actually lies. By contrast, in the working conditions and in the applications for the method and the system according to the present application, a master image is not suitable. Both the type of package and the print to be printed are often changed, often several times a day. With the method and the system of this invention, a highly flexible manner of working is obtained which, given this manner of inspecting, makes adaptation, conversion, or readjustment of a processing mode redundant. Also when applied for cleaning food products, this method is highly suitable because the setting of a dirt recognition model and the teaching-in thereof, to be regarded as a master image procedure, are obviated.

According to an extra advantageous elaboration of the invention, the selection criterion is chosen for an image in gray values with the criterion comprising a gray value. According to an alternative extra advantageous elaboration of the invention, the selection criterion is chosen for an image in color values whereby for each applied color a corresponding color selection criterion is included and the color selection criterion comprises a color value.

According to a further elaboration of the invention, a part of the image field comprises an optical marking which is used as reference. It is then preferred that in the before-image at least an edge part of the optical marking is used as reference. According to a further elaboration, the surface area of the edge part mentioned can be determined and be compared with a pre-set surface area limit value. Furthermore, it is advantageous if the before-image and the after-image are superposed one on the other, whereby shifts that have occurred during the treatment are established. According to an extra advantageous elaboration of the invention, the method comprises a pre-processing step whereby, of the before-image and of the after-image, a well-defined pixel area for visualizing the treated material piece is established, whereby at least the pixels in the image belonging to the treatment unit are removed. The treatment can comprise, for example, printing, and be carried out on a substantially plane material piece.

Further, the invention provides a system for printing information or figures on package units for food products, for example, but not exclusively, cartons of eggs, for example a system configured for carrying out a method according to the invention, wherein the system comprises:

- a sorting machine for sorting the food products,

- at least a single conveyor for supplying package units,

- at least a corresponding single transfer unit for transferring sorted products into such package units for filling them, and

- at least a corresponding single discharge conveyor for discharging such filled package units in a discharge stream,

wherein the system furthermore comprises for / at the at least single discharge conveyor:

- a unit for printing the information or figures, whereby each package unit is provided with at least a single print, and

- a detection system for inspecting the print. In this manner the above-mentioned advantages can be achieved.

Furthermore, an aspect of the invention concerns a system for cleaning eggs, the system comprising:

- a sorting machine for sorting eggs supplied as a stream of eggs,

- a cleaning unit for the eggs of this stream, for example, but not exclusively, a washer-dryer combination,

- an inspection unit for inspecting the cleaning carried out, whereby images or scans are obtained,

- a central processing unit for processing the scans, whereby acceptance labels or non-acceptance labels are obtained, and - an egg take-out unit for taking out of the stream the eggs for which non-acceptance labels have been issued,

wherein the inspection unit makes an image or scan of each egg at least two times, prior to cleaning and following cleaning, respectively.

The system can be applied, for example, for carrying out a method according to the invention, and can present the above-mentioned advantages.

Further elaborations of the invention are described in the subclaims.

Hereinbelow, the present invention, that is, the method and the system for inspecting treatment of an organic or inorganic material piece of for example a food product or of a package unit, more particularly of a predetermined part thereof, whereby for example information is applied or removed, will be elucidated in detail with reference to a drawing, in which FIGURE 1 schematically shows in side view an exemplary embodiment of the system according to the invention for inspection of printing;

FIGURE 2 shows a top plan view of the exemplary embodiment of

FIGURE 1, with FIGURE 1 being a view in the viewing direction II in FIGURE 2, and FIGURE 2 being a view in the viewing direction I in

FIGURE 1;

FIGURE 3 represents a flow diagram of an exemplary embodiment of the method for inspecting printing according to the present invention;

FIGURE 4 shows, more particularly, combinations of, in each case, two partial figures, each combination separately indicated with 4A, 4B, 4C, 4D, and 4E, a succession of steps in an exemplary embodiment of image detection, in particular of an image shift, following an edge detection step;

FIGURE 5 schematically shows an example of a system with sorting machine, printing unit and discharge conveyor; and

FIGURE 6 schematically shows an example of a system for cleaning eggs. In the FIGURES the same or similar numerals and symbols designate the same or similar parts and features. In an exemplary embodiment for, in particular, inspection of printing according to the present invention, FIGURE 1 shows in side view a package unit 1 under a printer head 2 and near a camera 3 with lighting unit 4 and camera sensor portion 5.

To one skilled in the art it will be clear that many types of cameras 3 and lighting units 4 can be applied. Where the hghting unit 4 is concerned, the purpose is to use a lighting that prevents in particular distortion and shadow formation.

In FIGURE 2, in a top plan view facing in the direction indicated by a viewing line (with arrows) I in FIGURE 1, the printer head 2, 2' is shown in two successive positions, being respectively a first position 00 in which the camera 3 makes an image prior to printing, a before-image, and a second position 20, represented in FIGURE 2 in broken lines, in which the camera 3 makes an image following printing, an after-image.

Likewise, FIGURE 1 is a side view facing in the direction indicated by a viewing line (with arrows) II in FIGURE 2.

In both FIGURES 1, 2 there is indicated a transport direction T for a conveyor, for example a belt conveyor (not represented in FIGURES 1, 2). Also represented, with a double arrow P, is the path followed by the printer 2 during printing. In this example, this path is at right angles to the transport direction T.

In the usual manner, FIGURES 1, 2 show the package unit 1 in a substantially horizontal orientation, with the belt conveyor accordingly following a substantially horizontal path. In FIGURE 3 there is schematically represented, in the form of a flow diagram, a sequence of steps of an exemplary embodiment of a method according to the present invention, in particular during use of the system (e.g., the system shown in FIG. 1). In the exemplary embodiment described here, use is made of the earlier-mentioned optical marking to check for possible shifts that may occur during the movements mentioned. The steps that are shown in this flow diagram are general indications, which is to say that in this area of technology there are typically multiple ways of implementing such a step.

In FIGURE 3, block 00 denotes an initial step in a method according to the present invention, namely, the making of a before -image at standstill of the package unit 1.

Thereupon, in block (step) 10 a print is made, with the printer 2 moving over the package unit 1 as for instance indicated in FIGURE 2.

In block (step) 20 an after-image is made of the print that has been made in block 10.

During these steps, the product or the package unit on which printing is done usually does not change in position. In particular, the conveyor, which carries the package unit, can, to that end, be kept stationary during these steps 00, 10, 20.

Block 30 is a first step in the process of processing the image made with the camera 3. More particularly, with the step in block 30 the image field is selected that is the most suitable for inspection of the print.

After the step of block 30 has been carried out, in a next step, according to block 40, it is established whether in the image field estabhshed in block 30 an optical marking is present which can be used as reference in further follow-on steps. This step in block 40, for the exemplary embodiment described here, is herein called an edge detection step.

More particularly, reference is made to an edge detection step to thereby indicate whether a well-defined part of the optical marking in the

before-image has been brought into vision sufficiently clearly or, stated differently, whether the image, and hence the above-mentioned well-defined part thereof, is suitable to function as a beacon or reference in the further follow-on steps.

Because in the processing of, for example, the many package units, multiple designs and types thereof may pass, not always a marking will be used, and it consequently does not need to be taken into account in printing, i.e., the accurate positioning of a print. Moreover, very gradually blending colors or grays will not need to be, or cannot be, acknowledged as edges.

For methods with which edges in images are determined, reference is for instance made to 'Comparison for Image Edge Detection Algorithms', Lin Bi et al., IOSR Journal of Computer Engineering, Volume 2, Issue 6 (July - Aug. 2012), pp 01-04, in which the well known methods such as named Canny, Sobel, Prewitt and Roberts are explained and compared to each other.

In follow-on block 50, in the case where the optical marking is present, the edge parts from the before-image and from the after-image are compared with each other. More particularly, the differences between these images are determined by establishing the overlap in terms of a number of pixels when the images are laid one onto the other. To one skilled in the art it will be clear that in an ideal situation, that is, where the positions of all factors, the instruments and the product to be printed remain the same, these images, where their optical markings are concerned, will fall onto each other with an exact fit.

More particularly, the so-called subtraction method is applied, whereby the intensity values (for example, values 0 or 1) of the pixels of the after-image, 'after', are subtracted from those of the before-image, 'before', written as

¾ - a', with the result accordingly being 0 or 1. Further details are explained with reference to the example according to FIGURE 4.

In the case where it is established that the images have shifted relative to each other, an operation is carried out whereby the before-image and the after-image are shifted such that the picture elements are laid or positioned on each other One-on-one'. In FIGURE 3 this is indicated with Y, carried out in a next step according to block 60.

In a generally known manner, for such determination of yes/no, Y/N, shifting, decision rules have been drawn up, for each product, here a package unit, or also an egg, separately.

Furthermore, the needed, and permitted or non-permitted, shift can give further information about the various settings of the system, which will be discussed with reference to signals 61, 62.

Hereinafter, for an explanation of the case where shifting according to block 60 is necessary, a symbol "T" has been chosen as edge part and this situation is hereinafter discussed in detail with reference to FIGURE 4. If the image of the edge part mentioned does not meet the criterion, then, following the arrow Y = YES, a shift, back to the original position, as indicated in block 60, is carried out.

If not, then, according to arrow N = NO, the after-image is subjected to a print test according to block 70. Hereinafter, with reference to FIGURE 4, an example of the manner of shifting according to block 60 will be explained in detail.

Furthermore, it will be indicated what further steps can be carried out when the shifting, and the result of the print test in block 70, become known at the arrows 61, 62, and 71, respectively.

When in block 60 it has been established that a shift is necessary, this also provides information about the reason or cause thereof, viz., the above- mentioned unwanted deviation in the movement paths of the belt conveyor and/or of the printer.

The processing of the signals according to block 60 is so configured that according to a signal 61, for instance, the positions of the

printer 2-camera 3 combination can be reset, and

that according to a signal 62, for instance, the settings and the drive of the belt conveyor can be checked and/or reset.

After a shift yes or no according to block 60 has taken place, in block 70 the (im)print itself is inspected. In block 70 the print is subjected to a so-called print test. Here, too, the images are processed according to the subtraction method, 'b— a', whereby the difference should not fall below a minimum value for pixel intensities, pre-set as a criterion, a print criterion. These pixel intensities can be determined and calculated in a known manner. More particularly, such determinations and calculations may be carried out. for instance, in each applied color separately, in combinations of these colors, after conversion of the colors to grayscale values, and furthermore per pixel position, or also after grouping of particular image positions or coordinates, or even overall.

Following the print test according to block 70, a next step is initiated with a signal 71. On the basis of this signal 71, to be regarded as an accept-signal when the print criterion has been met, as a non-accept signal when such is not the case, the product or package unit will be further processed, or be rejected and may be taken out of the stream of products. More particularly, provision may be made for, for instance, either packing and printing all over again, or placement back into the stream and providing a new print (for instance via a return unit RE).

With the help of the FIGURES 4A - 4F the step according to image processing block 60 in the flow diagram according to FIGURE 3 will be explained in detail.

More particularly, the FIGURES 4A - 4F each consist of two partial figures belonging together. In these FIGURES 4A - 4F, a symbol, here the letter "T", is shown, in different hatchings for clarity,

- in a left' hatched (135°) before-image,

- in a 'right' hatched (45°) after-image, the symbols not overlying each other to signify that in the interim of printing the print a shift has taken place,

- and finally, in each case in the right-hand partial figure, in black, as the result of superposition of the hatched symbols one on the other.

The manner in which the images have been laid one over the other will be explained hereinafter.

The symbol drawn here is a part of the optical marking, in respect of which, as explained hereinabove, it has been established by means of edge detection whether a shift has indeed occurred.

In FIGURE 4F an X-Y coordinate system is drawn to enable the shift shown in the grids of FIGURES 4A - 4E to be defined in detail.

Clearly, the step-by-step plan shown and followed in these FIGURES 4 is an exemplary embodiment for which in this field of technology, as known to one skilled in the art, many alternatives are known. Upon comparing the partial figures in FIGURE 4A, it will be clear that the after-image has been printed shghtly to the left, down, and hence has shifted relative to the before-image.

In a first step according to the partial figures in FIGURE 4B, the grids are laid one on the other, without shifting, and it is considered what quantity of pixels remains when, as already explained above, the after-image is subtracted from the before-image, 'before - after', 'b-a', whereby, starting from pixels which, with imprints, all have intensity , and, with imprints failing, have an intensity 'Ο', 30 pixels remain, or, to put it differently, 30 of such units. It will be clear that, ideally, that is, if no shifting had been necessary and the symbols in this step could have been placed exactly one on the other, 'b-a' would have left a remainder of 0 pixels.

In the steps according to the partial figures of FIGURE 4C the grid of the after-image is shifted relative to the grid of the before-image (and thus also the images themselves), over grid units X and grid units Y as indicated schematically for clarity in FIGURE 4F, over a distance -1 in the X direction and a distance + 1 in the Y direction. The remainder of pixels or units after 1b-a' is now 26.

As can be seen in the partial figures of FIGURE 4D, the shift in the X direction is +2 and in the Y direction +3, resulting in a remainder of 16 pixels or units after 'b-a'.

Finally, in the partial figures of FIGURE 4E a shift has been applied, of -3 in the X direction and +2 in the Y direction, whereby the symbols are positioned exactly one on the other and the remainder is 0 pixels or units. To one skilled in the art it will be clear that there are many possible sequential orders with a step -by-step plan to obtain one-on-one shifting. In this field of technology, often a method is utilized whereby at a level n a grid of n² pixels is chosen in the after-image and whereby in successive steps of n pixels, this after-image is shifted over the before-image, and the residual pixels are determined each time. In this methodology, thereupon the levels n are lowered, in a usual manner from 3 to 2 to 1, whereby decision rules or hnes yield the eventual match.

As will appear from the above, the processing of such package units is applied in, for instance, systems for packing, or sorting and packing, of food products, where printing of the products or printing of the package units, or even both, may be involved.

The present exemplary embodiment mainly relates to a system for processing eggs, but is also very suitable for other food products such as fruit, vegetables (peppers, cucumbers, tomatoes), or also meat. The system is configured in particular for carrying out a method according to the invention. Figure 5 shows schematically an example of such a system. More particularly, this concerns a system for printing information or figures on package units (not shown in FIG. 5), the system including:

- a sorting machine 106 for sorting the food products (not shown in FIG. 5),

- at least a single conveyor 107 for supplying package units,

- at least a corresponding single transfer unit 108 for transferring sorted products into such package units for filling them, and

- at least a corresponding single discharge conveyor 109 for discharging such filled package units in a discharge stream (in transport direction T);

wherein according to the present invention the system furthermore comprises at the at least single discharge conveyor 109,

- a unit 102 for printing the information or the figures whereby each package unit is provided with at least a single print, and - a detection system (inspection unit) 105 for inspecting the print.

The printing unit 102 and the detection system 105 (here represented as an integrated system) may for instance be implemented in the same way as the example shown in Figures 1, 2 (with camera 3 and printer 2) or in a different way.

According to an extra advantageous design of the system shown in FIGURE 5 the inspection unit 105 makes an image or scan of each package unit at least two times, viz., at least an image or scan prior to printing and at least an image or scan following printing.

Further, it is preferred that the system comprises a take-out unit UE for taking out of the discharge stream package units whose print does not meet a pre-set criterion.

FIGURE 6 shows an exemplary embodiment according to another aspect of the invention, viz., of a system for cleaning eggs. The system comprises a sorting machine 206 for sorting eggs supplied as a stream of eggs (not shown), a cleaning unit W for the eggs of this stream, for example, but not exclusively, a washer- dryer combination,

- an inspection unit 205 (in this case as part of the cleaning unit W) for inspecting the cleaning carried out, whereby images or scans are obtained,

- a central processing unit K for processing the scans, whereby acceptance labels or non-acceptance labels are obtained, and

- an egg take-out unit EU for taking out of the stream the eggs for which non-acceptance labels have been issued.

With great advantage, the system is so configured that the inspection unit 205 makes an image or scan of each egg at least two times, prior to cleaning and following cleaning, respectively (i.e., at least lx before cleaning, and at least lx after cleaning). The take-out unit EU may be implemented in different ways, and may preferably comprise a robot. Preferably, such system (for example a system schematically shown in FIG. 5 or FIG. 6) furthermore comprises a return unit RE (drawn-in in FIG. 6) for returning into the discharge stream the treated products, for example package units, food products, more particularly eggs, that have not met the criterion mentioned, in order for them to be treated anew.

It will be clear that the control of a system as described above and the processing of all data playing a role articularly in printing will be carried out by a central processing unit. In general, this concerns a central computer, personal computer, laptop, or even a tablet, placed in a rack or on a mobile console, which can be positioned at will, in most cases near one of the system parts mentioned. Such a processing unit will mostly make a connection with a server, via an internet connection or not so.

For the control of particularly the printing, as well as the processing of the image data or vision data, in a suitable manner the processing elucidated above is applied.

As mentioned earlier, such a system will advantageously comprise a take-out unit, and/or a return unit for such package units.

Both take-out and a return will preferably be automated. Where the direct connection to belt conveyor parts is concerned, this will be implemented in a manner known per se. Also, for such processing steps, robots may be deployed. In addition, robot grippers for such a purpose may be so configured that vision and print are incorporated in a gripper arm. To one skilled in the art, it will be clear that various modifications are possible of what has been described above, and is defined in the appended claims, in particular modifications that are understood to be within the scope of protection of the appended claims. For instance, the material pieces may be substantially plane or slightly curved, more particularly slightly convex. Furthermore, it is reiterated that in the case where no optical marking is applied, the edge detection step and any consequence thereof according to steps 40, 50, 60 cannot be carried out and only the print test 70 applies.

The method according to the present invention and the step-by-step plan according to the exemplary embodiment as described above can be deviated from in different ways within the scope of protection of the appended claims.

To one skilled in the art it will be clear that a plurality of cameras for imaging may be deployed. This will be the case especially where cleaning is concerned, both in connection with the intervening path to be traversed for cleaning, and in view of possible movement, such as rotating and tilting, of products such as eggs.

Further, it will be clear that a conveyor as mentioned may be implemented in different manners, for example as a belt conveyor as mentioned above or in another manner.

Claims

1. A method for inspecting treatment of an organic or inorganic material piece of for example a food product or of a package unit, more particularly of a predetermined part thereof, whereby for example information is applied or removed,

wherein the method, for example but not exclusively, comprises:

- inspecting of the printing of for example information or of a figure whereby a printing unit as treatment unit moves along a printing path over the material piece and applies thereto said information or figure whereby a print is obtained; or

wherein said material piece is stepwise conveyed along a transport path on a conveyor, for example belt conveyor, moving in a transport direction T, wherein the method furthermore, for each successive material piece, successively comprises:

- at standstill of said material piece near the treatment unit:

- choosing as image field said part of said material piece that is intended for treatment, for example printing or cleaning,

- making, with at least a single camera, a first image of said part prior to treatment, this first image or the before-image being composed of pixels, and whereby for each pixel first image signal values are obtained,

- treating said material piece, and - making a second image or after-image of said image field after completion of the treatment, whereby second image signal values are obtained, and

- thereupon comparing the first image signal values with the second image signal values whereby for each pixel of the images difference values are obtained, the difference values of the pixels corresponding to those of the treated material piece being unequal to 0,

characterized in that

the method furthermore comprises inspecting the treated material piece whereby said intensity difference values are established for the pixels of said images, while a well-defined combination of these difference values is taken as a selection criterion for the decision about the complete or partial presence, or absence, of the treatment of said material piece.

2. The method according to any one of the preceding claims, characterized in that the selection criterion is chosen for an image in gray values, wherein the criterion comprises a gray value.

3. The method according to claim 1, characterized in that

the selection criterion is chosen for an image in color values, wherein for each color applied a corresponding color selection criterion is included and wherein the color selection criterion comprises a color value.

4. The method according to claim 1, 2, or 3, characterized in that

a part of the image field comprises an optical marking which is used as reference.

5. The method according to claim 4, characterized in that

in the before-image at least an edge part of the optical marking is used as reference.

6. The method according to claim 5, characterized in that the surface area of said edge part is determined and is compared with a pre-set surface area limit value.

7. The method according to claim 6, characterized in that

the before-image and the after-image are laid on each other, wherein shifts that have occurred in treatment are established.

8. The method according to any one of the preceding claims, characterized in that

the method comprises a pre-processing step whereby, of the before-image and of the after-image, a well-defined pixel area for visualizing the treated material piece is established while at least the pixels in the image belonging to the treatment unit are removed.

9. The method according to any one of the preceding claims, characterized in that

treatment comprises printing and is carried out on a substantially plane material piece.

10. A system for printing information or figures on package units for food products, for example but not exclusively cartons of eggs, for example a system configured for carrying out a method according to any one of the preceding claims, wherein the system comprises:

- a sorting machine for sorting said food products,

- at least a single conveyor for supplying package units,

- at least a corresponding single discharge conveyor for discharging said filled package units in a discharge stream, characterized in that

the system furthermore comprises for said at least single discharge conveyor,

- a unit for printing said information or figures, while each package unit is provided with at least a single print, and

- a detection system for inspecting said print.

11. The system according to claim 10, characterized in that

the inspection unit makes an image or scan of each package unit at least two times, prior to printing and following printing, respectively.

12. The system according to claim 10 or 11, characterized in that

the system comprises a take-out unit for taking out of the discharge stream package units for which said print does not meet a pre-set criterion.

13. A system for cleaning eggs, for example a system configured for carrying out a method according to any one of the preceding claims 1-8, the system comprising:

- a sorting machine for sorting eggs supplied as a stream of eggs,

- a cleaning unit for the eggs of this stream, for example but not exclusively, a washer-dryer combination,

- a central processing unit for processing the scans, whereby acceptance labels or non-acceptance labels are obtained, and

- an egg take-out unit for taking out of the stream the eggs for which non-acceptance labels have been issued,

characterized in that

the inspection unit makes an image or scan of each egg at least two times, prior to cleaning and following cleaning, respectively.

14. The system according to claim 12 or 13, characterized in that the take-out unit comprises a robot.

15. The system according to any one of claims 11-14, characterized in that the system furthermore comprises a return unit for feeding back into the discharge stream the treated products, for example package units, food products, more particularly eggs, that have not met said criterion, in order for them to be treated anew.

16. System for treating food products such as, for example, but not exclusively, eggs, package units for food products such as, for example, but not exclusively, cartons of eggs, in accordance with the method according to any one of claims 1-9.

17. The system according to any one of claims 10-16, characterized in that at least a single camera is used for said inspecting.