Patent Application
20130056398
The current invention relates to a method and apparatus for inspecting a stream of products. This inspection can further result in a quality selection by means of a sorting step.
The invention is applicable when removing certain degraded products and foreign objects from an incoming stream of products.
The invention is particularly suited for sorting food products such as green beans, peas, nuts, raisins, cauliflowers, lettuce and such like for which non-food products such as wood, plastics, glass and others need to be removed from the stream of products.
The invention is furthermore extremely suitable for sorting non-food products such as plastics from recycling garbage, sorting of glass and such like.
It is known from the international patent application WO 01/00333 that product objects in a stream of products can be illuminated with a concentrated beam of light. The reemitted light is captured by a detector whereupon it is analyzed. Based on this analysis a selection mechanism can be controlled to achieve a certain sorting result.
In the absence of product, the light is reflected by a background element that needs to be chosen product dependently. More specifically, the background needs to be chosen such that it shows the optical characteristics of good product. In other words, the good product is invisible against the background. However, deviations in an analyzed product such as insect bytes, putrescent stains, foreign objects and such cause a deviation in the returned light signal. By adjusting a threshold one can make the difference between the light signal coming from the background and acceptable products on the one hand and the light signal coming from unacceptable product to be removed on the other hand.
Similar background elements are described in the American patent U.S. Pat. No. 4,723,659 and the European patents EP1012582 and EP0443469. Generally speaking it concerns a background element positioned perpendicular to the direction of product movement, in the field of view of the detecting means. Usually the background element is a cylindrical roller. While rotating and with the aid of a scraper it becomes self-cleaning.
A disadvantage of this method is that for each kind of product a specific background element needs to be available. Thus a background element for carrots should have an orange color, while for green beans it should have a green color. During the sorting of food products and more specifically while switching from one product to another, it is required to switch the background element as well. Furthermore, the cost of a background element is not negligible.
In certain applications the background element is given additional optical properties. Many fresh vegetables contain for example chlorophyll. A frequency shift towards the infra-red spectrum occurs within these molecules when illuminated with light having a wavelength between 640 and 680 nanometer. This emission phenomenon is called fluorescence. By giving the background element the same fluorescent properties one can, in the state of the art, additionally sort based on the presence of chlorophyll in the analyzed products. Other molecules, such as aflatoxin, show fluorescent properties as well and could in principle be detected in the analyzed products according to a similar technique.
An important disadvantage is that over time these kinds of background elements loose their fluorescent properties. This has adverse effects on the sorting quality and is also uninteresting for the users of such equipment.
For these reasons there is a need for a sorting device, in particular an inspection device, without the disadvantages of the devices known in the state of the art.
For these reasons there is need for a method not showing the disadvantages of the current state of the art.
In general the object of the invention is a method and apparatus to carry out a selection between products in a large, continuous stream of products in a very effective, reliable and cost-effective way.
More specifically, according to a number of preferred embodiments, the invention aims at an inspection method and inspection means avoiding the replacement of the background element during a product switch.
In other words, the object of the invention is an inspection method and inspection means using a background reference which is at least product domain independent.
The invention is related to an apparatus for sorting a stream of products, comprising:
According to an embodiment, said apparatus further comprises means for generating a location signal which is indicative of the location of the products, by detecting the immediate incidence of light on the background element.
According to an embodiment, said detection unit is a camera arranged to capture an image of the scanning zone.
According to an embodiment, the background element is an optical fiber with a grooved surface for capturing the incoming light.
According to an embodiment, the background element is a manifold of detectors configured to convert the incident light into an electric signal.
The invention is further related to a method for sorting a stream of products in products to be accepted and products to be rejected comprising the steps of:
According to an embodiment, generating the location signal further comprises detecting and converting that part of the concentrated scanning light beam, which is which not obstructed by the products, thus obtaining a signal that is indicative of the location of the scanned products.
According to an embodiment, the background element is an optical fiber with a grooved surface for capturing the incoming light.
According to an embodiment, the background element is a manifold of detectors configured to convert the incident light into an electric signal.
The invention is also related to an apparatus for sorting products according to the method of appended claim 6, comprising:
According to an embodiment, said means for generating a location signal are configured to generate said location signal based on the immediate incidence of light on the background element.
According to an embodiment, this background element is an optical fiber with a grooved surface for capturing the incoming light.
According to an embodiment, the background element is a manifold of detectors configured to convert the incident light into an electric signal.
The invention is equally related to an apparatus for sorting a stream of products, comprising:
According to an embodiment, the background element is an optical fiber with a grooved surface for capturing the incoming light.
According to an embodiment, the background element is a manifold of detectors configured to convert the incident light into an electric signal.
The invention is also related to a method for sorting a stream of products in products to be accepted and products to be rejected comprising the steps of:
According to an embodiment, the background element is an optical fiber with a grooved surface for capturing the incoming light.
According to an embodiment, the background element is a manifold of detectors configured to convert the incident light into an electric signal.
The method of sorting products according to the invention is characterized at least by transporting the products to sort along a certain trajectory in the form of a product stream having a width; a background element extending along the width of the product stream; with a concentrated light beam illuminating along the width of the product stream, the products to sort and, in absence of said products, the background element; capturing the light reemitted by the products and the background element; based on said observed light carrying out a first selection between the background element on the one hand and all the products in the product stream on the other hand; carrying out a second selection between the products to sort on the one hand and the products to be rejected on the other hand and based on this second selection automatically carrying out a separation of the products in said product stream.
Preferably the background element comprises a surface extending along the width of the product stream, whereby said surface reflects the incoming light at least partially.
In a particularly useful embodiment the background element has the shape of a cylindrical roller.
In an alternative embodiment the background element comprises means to capture and redirect the incoming light towards an opto-electrical convertor. In this case such a background element generates a signal having a progression from which the presence or absence of products in the scanning zone can be easily deduced. A thus obtained Boolean signal is particularly useful in the method according to the invention.
The first selection is preferably done based on whether or not the intensity of the detected light or a derived signal thereof crosses a threshold value.
In certain cases, more specifically when the total range of products features positive as well as negative peaks against the background signal, the first selection is done based on whether or not the intensity of the observed light emitted by the background element or a derived signal thereof falls within a zone, said zone further characterized by a maximum threshold value.
The second selection is preferably done based on whether or not the intensity of the detected light or a derived signal thereof crosses a threshold value.
In a preferred embodiment said crossing of a threshold value is exclusively defined within those zones which are labeled during the first selection step as originating from product.
In an exceptionally preferred embodiment a new signal is generated after the first selection, further characterized by preserving the intensity of the observed light in those zones outlining product (the product zones) and subsequently changing the intensity in the zones where the background element can be observed to another level.
Additionally it is preferable to filter said signal such that the high-frequency transitions at the product zones are flattened and a new signal is created. Said filter could for example be an adaptive filter specifically tuned to smooth the transition from product zone to background zone and vice versa.
In the most practical embodiment according to the invention the second selection is done on said filtered signal.
In any case the selection of the background element will be such that it leads to at least one corresponding signal having a path according to which a first selection can be carried out between said background element on the one hand and all products in the product stream on the other hand.
In a practical embodiment of the method according to the invention the scanning is done using a rotating mirror, preferably a fast rotating polygonal mirror.
In a very practical embodiment the scanning uses a laser beam.
In a practical embodiment the products are transported on a vibrating table, belt or suchlike, towards an inspection installation.
In some cases, more specifically in the case of free-fall sorting devices, the products are further guided during their free fall by a free-fall plate. Furthermore, the products to separate are segregated by means of a manifold of air valves positioned along the width of the product stream and opened based on the second selection step.
In some cases, more specifically in those cases where defects are situated on both sides, it is advantageous to scan the products to sort from two sides, opposite from each other.
The method could be combined with color sorting by sorting based on light reflections.
Additionally different concentrated light beams having each a different wavelength, possibly combined into one bundle, could be utilized.
In an important variant according to the invention two signals are combined in a two-dimensional graph such that each point in this graph corresponds with a specific intensity level according to the path of the first signal combined with a specific intensity level according to the path of the second signal; the points corresponding with the product to be accepted are grouped in first zone; the points corresponding with products to reject are grouped in a second zone; the points corresponding to the background element are outlined by a third zone; adjusting the level of the background signal is realized by repositioning the third zone to a new location.
In this case moving said third zone can be achieved by visualizing this zone in a graph displayed in a graphical user interface and subsequently dragging this zone to a new location.
In a preferred embodiment this said new location is chosen such that a separation can be made between the first and the third zone on the one hand and the second zone on the other hand using a separation plane.
Additionally more than two signals can be combined into a more-dimensional graph.
Apart from said method, the invention also refers to an apparatus to sort products using this method and such that it comprises at least a transport device to transport a stream of products, extending over a width, into a specific direction; means to scan the products to sort along the width of the product stream, further comprising means to generate a concentrated light and direct it towards means to cast this light beam onto the products; means to capture the returning light; means to carry out a selection between the scanned products based on the observed light; means to separate the products based on this selection.
In a preferred embodiment the means to generate the concentrated light is a laser generator.
In a preferred embodiment the means to cast the light beam onto the products comprises optical means, more specifically a rotating polygonal mirror, moving the concentrated light transversely across the product stream. The current invention is however not limited to such a scanning arrangement. It could, by way of example, as well generate a row of concentrated light beams, possibly turned on and off in sequence.
Additionally the means to carry out a selection based on the returning light could be based on digital electronic components, more specifically Field Programmable Gate Arrays and microprocessors, or could be based on analogue electronic components such as operational amplifier circuits, or it could be a combination of analogue and digital processing units.
In a practical embodiment the means to make a separation between the products based on said selection are composed of a manifold of air valves, mounted transversely across the product stream.
In an advantageous embodiment the background element is composed of a surface across the width of the product stream, such that the incident light is at least partially reflected by said surface.
In an alternative embodiment the background element is composed of means that capture and channel the incident light towards means to convert this light into an electric signal.
In a preferred embodiment the means to capture the returning light are composed of an optical filter making the detection arrangement sensitive for a specific light spectrum, in operable communication with a spatial filter making the detection arrangement sensitive for a specific zone of the returning light, and in operable communication with both filters an opto-electrical converter transforming the light into a corresponding electric signal.
A method for sorting a stream of products in products to be accepted and products to reject comprising the steps of moving through a scanning zone the products to sort, supplied in a product stream spanning a certain width and having a thickness of substantially a single layer of products, in this scanning zone linearly scanning one or more concentrated light beams across the width of this product stream, illuminating, in the absence of products, a background element positioned behind this product stream that extends over the width of it, whereby this light beam produces light signals at these scanned products and at this scanned background element, detecting these light signals whereby these light signals are converted in electric signals, generating one or more control signals on the basis of these converted signals whereby these control signals allow making a selection between the scanned products to be accepted on the one hand and the scanned products to be rejected on the other hand, and sorting the product stream by means of these one or more control signals, characterized in that this method further comprises; choosing this background element) such that the corresponding detected light signal differs in at least 1 parameter from the light signals of the products to sort and whereby generating one or more control signals further comprises shifting the background level of the converted signals after detection of the light signals, towards a new signal level chosen such that, in the thus obtained signal, the signal level of the signal of a scanned product to be accepted differs from the signal level of a scanned product to be rejected. The parameter in which the background element can differentiate itself from the products to sort can be the signal level, a spatial aspect such as scattering or a frequency aspect such as color information.
This method can further comprise, after moving the background level of the converted signals, comparing the thus obtained signal with one or more threshold values to generate in this way the one or more control signals.
Moving the background level according to this method can further comprise generating a signal which is indicative of the location of the scanned products in the detected and converted signals and shifting the level of the converted signals to locations other than these of the scanned products such as have been indicated by this location signal.
Generating the location signal according to this method can further comprise detecting and converting the light signals originating from the scanned background element and from the scanned products, in these converted signals separating the signal originating from the scanned background element from the signals of the scanned products such that a signal is obtained indicative of the location of the scanned products.
Distinguishing the signal originating from the scanned background element according to this method can further comprise comparing the converted signals with one or more threshold values.
In an alternative embodiment of these methods generating the location signal can further comprise detecting and converting that zone of the concentrated scanning light beam passed by the products, as such obtaining a signal that is indicative of the location of the scanned products.
The location signal in the different embodiments of this method can be a Boolean signal. Shifting the signal level to a new signal level can then happen according to the formula D=BC+s(C⊕1), in which B is the detected and converted light signals, s a real number chosen in function of the desired shift of the signal level, C the location signal, and ⊕ defined as the modulo-2 addition.
The location signal in the different embodiments of this method can be a Boolean signal. Shifting the signal level to a new signal level can then happen according to operation D=B when C=1 and D=0 when C=0 and in which B is the detected light signal, and C is the location signal.
The location signal in the different embodiments of this method can be an analogue or digital signal, whereby comparing the thus obtained signal with one or more threshold values happens only on the location of the scanned products as indicated by the location signal.
The background level of the converted signals can be shifted towards a signal level according to that of a product to be accepted.
The location signal in any embodiment can be generated on the basis of one or more first detected signals and afterwards used to indicate the location of the products in one or more second detected signals.
The background element in any of the embodiments can consist of a surface that extends over the width of the product stream, whereby said surface at least partially reflects the incident light. Preferably this background element has the shape of a cylindrical roller.
In an alternative embodiment this background element consists of means to capture and redirect the incident light towards a opto-electrical convertor. In this case the background element can be an optical fiber with a grooved surface to capture the incoming light. Such optical fiber can consist of segments, whereby for each segment the orientation of these grooves with respect to the longitudinal direction of the optical fiber is chosen in function of the position of this segment along the width of the product stream.
In any embodiment according to this method the thus obtained signal can be filtered prior such that the high-frequency transitions near the product zones are flattened, generating a new filtered signal. This filter can be an adaptive filter which is adjusted specifically to smooth the transitions from a product zone to a background zone and vice versa.
In any embodiment according to this method the linear scanning of the product stream can happen by means of a moving mirror, preferably a rapidly rotating polygonal mirror. The product stream can be scanned by several concentrated light beams by means of this moving mirror, whereby every light beam has a separate frequency. Preferably this concentrated light beam is a laser beam. The products to sort can be scanned from both edges of the product stream.
In any embodiment of this method the supply of the product stream can happen by means of a vibrating table, a conveyor belt or suchlike. The products can further be supplied by means of a free-fall plate which guides these products during their free fall towards the scanning zone.
In any embodiment of this method the sorting of the product stream by means of these one or more control signals can happen by controlling a manifold of air valves positioned across the width of the product stream by means of these one or more control signals.
In any embodiment, besides at the signal level, sorting the product stream can also happen on color, i.e., the frequency of the detected light signals.
In an embodiment of aforementioned methods whereby generating one or more control signals by means of moving the background level of the converted signals to a new signal level chosen as such that, in the thus obtained signal, the signal level of the signal of a scanned product to be accepted differs from the signal level of the signal of a scanned product to be rejected, further comprising; combining two detected and converted signals in a two-dimensional graph, in which each point corresponds with a particular intensity level according to the path of the first signal combined with a particular intensity level according to the path of the second signal; the points which correspond to product to be accepted are grouped in a first zone; the points which correspond to product to be rejected are grouped in a second zone; the points which correspond to the background element are outlined by a third zone; adjusting the level of the background signal is realized by repositioning the third zone to a new location. Moving said third zone can happen by visualizing this zone in a graph displayed in a graphical user interface and subsequently dragging this zone to a new location. This said new location can be chosen such that a separation can be made between the first and third zone on the one hand and the second zone on the other hand. This two-dimensional graph can have an additional dimension showing the histogram of appearing signal combinations. Furthermore, more than two detected signals can be combined with each other in more-dimensional graph so that, for every location in the scanning zone, as much as possible optical information is collected and depicted, allowing to make a better distinction between the location of the products to be sorted and these of the background on the one hand and between the products to be accepted and products to be rejected on the other hand. All or at least one of said first, second and third zones in such two or more-dimensional graph can be inferred by automatic clustering algorithms.
An apparatus for sorting products according to the methods of any of the previous claims, characterized by at least consisting of a supply system transporting a single layer of the products to be sorted along a certain trajectory in the form of a product stream extended over a width; means to scan to products to be sorted over the width of this product stream, whereby these scanning means further comprise; means to generate a concentrated light beam and direct it towards the products via optical means; means to detect the returning light and convert it to an electric signal; means to generate control signals enabling to carry out a selection between the scanned products based on said detected light; and means to sort the product stream based on said selection by means of said one or more control signals, characterized in that the sorting apparatus further comprises; a background element chosen such that the corresponding detected light signal differs in at least 1 parameter from the light signals of the products to be sorted and whereby the selection means comprise means to generate one or more control signals by shifting the background level of the light signals towards a signal level chosen such that, in the thus obtained signal, the signal level of a scanned product to be accepted differs from the signal level of a scanned product to be rejected.
The selection means of such sorting device can further comprise means to generate a location signal based on one or more detected signals, means to obtain a signal based on this location signal and based on these or other one or more detected signals, such that the background level in these last signals is shifted to a new level enabling to differentiate products to be accepted from products to be rejected in said obtained signal.
These selection means can further comprise means to compare the obtained signal with one or more threshold values, in this way generating the one or more control signals.
These selection means can further comprise filters to priefilter the thus obtained signal so that the high-frequency transitions close to the product zones are flattened and thus obtain a new filtered signal. This filtering operation can be achieved by means of an adaptive filter specifically adjusted to smoothing the transitions from a product zone to a background zone and vice versa.
In any of the aforementioned sorting apparatuses this background element can consist of a surface that extends over the width of the product stream, whereby said surface reflects the light at least partially. Preferably this background element has the shape of a cylindrical roller.
In an alternative embodiment this background element can consist of means to capture and redirect the incident light towards an opto-electrical convertor. Such background element can be an optical fiber with a grooved surface to capture the incident light. Such optical fiber can consist of segments, whereby for each segment the orientation of these grooves with respect to the longitudinal direction of the optical fiber is chosen in function of the position of this segment along the width of the product stream.
A laser can be used in such sorting apparatuses to capture the concentrated light beam. This laser can be moved across the width of the product stream by means of a rotating polygonal mirror.
In such sorting apparatuses the means to make a selection between the scanned products in function of the observed light consist of a signal processing platform based on digital electronic components, more specifically Field Programmable Gate Arrays and microcomputer processors, or based on analogue electronic circuits, such as op-amp circuits, or a combination of analogue and digital processing units.
In such sorting apparatuses the means to sort the product stream in function of said selection by means of these one or more control signals, consist of a manifold of air valves, positioned transversely across the product stream.
In such sorting apparatuses the means to capture the light can consist of an optical filter making the detector sensitive to a particular light spectrum; in operational communication with a spatial filter making the detector sensitive to a particular zone of the returning light; in operational communication with both said filters an opto-electrical convertor converting the light to a corresponding electric signal.
a and 3b show alternative embodiments of the background element.
a-e illustrate the method in several steps according to the current invention which results in a better or at least more advantageous inspection;
a-b illustrate this method in a two-dimensional representation;
a-f illustrate schematically the signal processing in an inspection device when the background element generates a signal that deviates from a good product
a-d illustrate schematically the processing of the signal according to an embodiment of the invention
a-d illustrate schematically the processing of the signal according to an embodiment of the invention
a-d illustrate schematically the processing of the signal according to an embodiment of the invention
a-c illustrate schematically the processing of the signal according to an embodiment of the invention
a-c illustrate schematically the processing of the signal according to an embodiment of the invention
The current invention will be described by means of a few examples, referring to certain figures, without any restrictive kind. The figures are only schematic and not limiting. In the figures, the dimensions of certain elements can be exaggerated or not in true proportion. This is because of illustrative considerations. For this reason, the dimensions and relative dimensions do not necessarily correspond to reality.
The current invention teaches a method and a mechanism for sorting products 2, 3, to be precise, granular products like raisins, beans, berries, but also plastic grains, that are conveyed in large quantities and in a continuous stream.
In addition, the method according to the invention is also suitable for inspecting larger products like broad beans, cauliflower, lettuce, etc.
The supply system 1 with width W can be a vibrating table, or any other conveyor system known in the current state of the art. In case supply system 1 is being executed as a conveyor belt, the use of a free fall glide 4 can be superfluous, as is well known by the person skilled in the art.
In the scanning zone 28, the inspection unit watches the falling product 2,3 by analyzing the returning light. In function of this analysis, a reject system 11 is being controlled. This results in a separation of the product stream in an accept stream 13 and a reject stream 12.
Behind the scanning zone 28, a background element 5 is illuminated and observed while no product is present 2,3 in that zone 28. The optical properties of the background element 5 are chosen in such a way that a proper distinction can be made between all products 2,3 in the product stream on the one hand and the background element on the other hand. These optical properties can refer to the frequency or to spatial properties of the background element 5. The background element can generate a light signal with another frequency or reflect the incident light 34 in another way, or even scatter it. This method differs from the current state of the art, which tries to make a distinction between all the products to be rejected 3 from the product stream on the one hand and the background 5 together with the products to be accepted 2 on the other hand. For this reason, in the current invention the choice of the background element 5 becomes considerably less complicated and independent of the product domain. For instance, the background element 5 will be the same for green beans and orange carrots. As opposed to the current state of the art, in which a specific background element for every product has to be available which has optical properties identical to those of the products to be accepted 2. In the case of green beans and carrots, the current state of the art would need two different background elements: one with a green color, and another with an orange color. When the products to be sorted 2,3 are transported by a conveyor belt 1, this conveyor belt can be used as background element to obtain a background signal that differs from the signal of all the products 2,3, as is described in the embodiments of the invention.
In a preferred embodiment of the current invention, the background element 5 is a cylindrical roller, to be precise, a rotating roller that cleans itself by means of a scraper that is placed against the roller.
In a preferred set-up for the sorting of fresh vegetables such as green beans, carrots and peas, the background element 5 is implemented as a white, strongly scattering, not fluorescing, cylindrical roller. With reference to
In an alternative version, the background element 5 is an intrinsic component of the mechanical construction and contains, besides the function of optical background, an additional function as mechanical support element. As a result, it can, as such, not be removed. Such greatly simplified mechanical embodiment according to the current invention is impossible to implement in the current state of the art.
The inspection unit 9,10 consists of a scanning unit 43 and a detection unit 44 (
When this light 32,33,34 inclides on a product 2,3 a zone of the light 46, 47, 48 will be reflected according to the color of this product 2,3. This makes color sorting possible.
Dependent on the light permeability of the illuminated product 2,3, the concentrated light beam 32,33,34 will be reflected directly and/or scattered, as is elaborately described in the American patent U.S. Pat. No. 4,634,881. This makes structure sorting possible. Additionally, the presence of fluorescing molecules in the product 2,3 will cause a frequency shift in the reflected light, making it possible to sort on the presence of those molecules, like chlorophyll and aflatoxin.
Entirely within the scope of this patent, various light beams with different wavelengths can be bundled, preferably by combining various lasers of different wavelengths by means of minors and optical filters.
In
As is illustrated in
In international patent application WO 2007/062219 and in zone 2 “Design and fabrication” of the article “A fiber grating based distributed light source”, by G. E. Carver, Proc. Of SPIE Vol. 6371, 63710H-2 (2006), both integrally enclosed in this description, a grooved optical fiber is used to obtain a linear uniform light source. Light injected in the optical fiber in its longitudinal direction, is redirected in a direction differing from the longitudinal through grooves in the side of the fiber. The redirected light can be further guided through a cylindrical optical system to obtain a more uniform light distribution within a restricted area. According to the choice of the geometric parameters of the grooves (cf.
Such optical fiber can, however, also be used to capture light originating from a linearly moving concentrated light beam 34 and to redirect it in the longitudinal direction of the optical fiber to an exit as illustrated in
As already mentioned in these publications, a grooved optical fiber of arbitrary length can be obtained by coupling separate segments (cf. SPIE article, chapter 2, last paragraph). Therefore, an optical fiber can be made that extends over de entire width W of the product stream. Accordingly, for every immediate position of the concentrated light beam, such a grooved optical fiber can capture the, in the absence of products, uninterrupted light 34 and redirect it to a detector 40.
Because the angle, formed by the uninterrupted light and the optical fiber used as background element 5 in
This can be prevented in two manners. As mentioned above, the optical fiber can consist of coupled segments. For every segment of the optical fiber, the orientation of the grooves can be kept the same. This can lead to an efficient production of these segments. Every segment in the optical fiber 5 can be placed under another angle, depending on the position according to the width of the product stream. A segment in the middle of the product stream will be placed in a substantially parallel position in relation to the product stream, while segments on the edges of the product stream are placed under an angle in relation to the product stream, correspondent to the angle formed by the light beam 34 and the product stream. Because of this variable orientation of the segments throughout the width of the product stream, the uninterrupted light 34 will always incide on the grooves under substantially the same angle and will be captured and redirected in the same way. Preferably, the segments are placed on an arc described by the concentrated light beam 45 when scanning the product stream.
As mentioned above, the optical fiber can consist of coupled segments. For every segment of the optical fiber, the orientation of the grooves can be changed. After all, the orientation of the grooves can be chosen separately for every segment by setting the relative orientation of the printer accordingly. The orientation of the grooves of a segment can therefore be adapted according to its position in relation to width of the product stream and to the angle formed by the inciding light beam 34 and the product stream at that point. In this embodiment of
An alternative as illustrated in
The signal on the exit of the detecting background element 5, as illustrated among others by
According to the invention, optical filters 36 can be used to render the detection unit 44 sensitive to one specific wavelength by placing this filter 36 into operational communication with abovementioned opto-electrical convertor 38.
According to the invention, a spatial filter 37 can be used to block or to let through certain zones of the returning light 46,47,48. For instance, a spatial filter 36 can be used, which only lets through the scattered light. Such spatial filters are described in the American patents U.S. Pat. No. 4,634,881 and U.S. Pat. No. 4,723,659.
In a preferred embodiment, the spatial filter 36 consists of a diaphragm that is placed right before the opto-electrical convertor 38.
As is schematically illustrated in
In a preferred embodiment, every detection unit 44, 44′ uses a different combination of optical 36 and spatial 37 filters. Because of this, every detection unit 44,44′ is sensitive to a specific zone of the returning light 46,47,48 having a specific wavelength. The output signals 39, 39′ are representative of a specific zone of the returning light 46,47,48 on a specific wavelength.
The first detection unit 44 generates a first electric signal 39 with a level determined by the abovementioned optical and spatial filters chosen for that detection unit. The second detection unit 44′ generates a second electric signal 39′ with a level determined by the abovementioned optical and spatial filters chosen for that detection unit. The detection units 44,44′ are in operational communication with the processing unit 41 via the signals 39,39′.
The processing unit 41 will perform a selection between the scanned products 2,3 and the background element 5, in function of the returning light 46,47,48, more specifically based on the electric signals 39,39′.
In a preferred embodiment according to the invention, the processing unit 41 is a digital processing platform based on Field Programmable Gate Arrays or microprocessors. The processing unit 41 could, however, also consist of analog op-amp circuits or a combination of analog and digital components as is known by the person skilled in the art.
An apparatus described in the previous paragraphs by combining a number of the above-described features is an apparatus 14 for sorting a stream of products 2, 3, comprising:
According to one embodiment, the detection unit 44 consists of one or more separate units 44/44′ as shown in
According to a preferred embodiment, the detection unit 44 is a camera, configured to capture images of the falling products as they are passing the scanning zone 28 in front of the background element 5. In other words, the camera captures an image of the scanning zone 28. In this embodiment, the background element 5 consists of means to capture incident light from the scanning unit and to direct it to a detector 40, or the background element consists of an array of detectors 40′ configured to convert said light into an electric signal (i.e. the background element is produced according to
The camera can be sensitive to (i.e. capable of detecting) the reflected laser light beams 46,47,48 reflected off the products and the background element. In this case the camera acts as a detection unit that is completely equivalent to the detection unit 44 shown in
The camera may be a CCD camera mounted suitably in relation to the product stream. A possible camera setup that is suitable for an apparatus according to this embodiment is shown in patent document WO2008/116924A2, incorporated herein by reference. The difference between an apparatus according to the latter embodiment and the apparatus of WO2008/116924A2 is that the background element in an apparatus of the invention consists of means to capture incident light from the scanning unit and to direct it to a detector means 40,40′ that is configured to convert said light into an electric signal 39. The detector means is either a detector 40 arranged to receive the light 56 from a grooved fiber as in
The method according to one embodiment of the invention, as is illustrated in
In the processing unit 41, the incoming signals 39,39′ can be combined into new signals A, B according to the formula:
A=n39+m39′,
B=p39+q39′
where n,m,p,q are real numbers and 39,39′ said input signals.
In an advantageous embodiment of the invention, factors m and p are equal to zero. This means in principle that no combination is made. In this case, detection unit 44 generates the signal A, and detection unit 44′ the signal B.
As an example, without any limitation to the scope, we consider a detection unit 44 having an optical filter 36 set to the light spectrum between 690 and 740 nanometers, more particularly the fluorescence spectrum of product 2 containing chlorophyll when illuminated between 540 and 680 nanometer. The signal A shows a possible path of such a set-up where a peak 16 is perceptible at the location of said product 2 containing chlorophyll.
The problem occurs when the signal level in zone 17, due to the products to be rejected 3, does not show a noticeable difference with the background signal 15. In that case, it is not directly feasible to make a distinction between the products to be rejected 3 on the one hand and the background element 5 together with the products to be accepted 2 on the other hand. Although this distinction must be made because only the products to be rejected 3 are allowed to give cause to a reject-action by means of a reject system 11.
In
The signal B, as illustrated in
On signal B, a zone 49 is defined in which the background signal 19 is situated. All zones 19 that are located within this zone 49, are labeled by the processing unit 41 as coming from the background element 5. To be precise, the zone 49 is determined by a maximum threshold value tmax and a minimum threshold value tmin. In an advantageous embodiment, these threshold values tmax, tmin can be adjusted by a user.
In order to better represent the next steps in the method according to the current invention, a Boolean signal C is introduced, whereby the value 0 is adopted at the locations of the background signal 54 and where the value 1 is adopted at the locations 18 outside the zone 49 on the signal B.
The current invention does, however, not exclude that in an alternative method, the Boolean signal C is effectively being generated or is directly available in the processing unit 41, for example in case of an embodiment as described in
In a possible next step, according to the invention, a new signal D is being generated using the formula:
D=AC+s(C⊕1),
wherein ⊕ is being defined as the modulo-2 addition.
In this way, the new signal D is an exact copy of the abovementioned signal A on places 20,21 of product 2,3. On the places where the background element 5 is being observed, a new value s is being established so that the background signal 22 clearly separates itself from the products to be rejected 3.
In the example described above, the path of signal A was interpreted as coming from the emission peak of a product 2 containing chlorophyll, against a non-fluorescing background. By generating the signal D, a distinction can be made between the background element 5 together with the products 2 containing chlorophyll on the one hand, and the products to be rejected 3 on the other hand, making it possible to automatically remove the latter products.
In a preferred next step, the signal D will be additionally filtered by, for instance, a low-pass filter, generating a new signal E. The low-pass filter is constructed according to known principles, for instance by means of digital multi-tap FIR filter. The cut-off frequency will be chosen in a way that the high frequency transitions on the edges of the zones 20,21 in the signal D are flattened sufficiently, without losing the actual signal content. In this way, one obtains the zones 24, 25, where the products 2,3 are, and zone 23, where the background element 5 is.
In an alternative form, the filtering is done by means of an adaptive filter that is tuned to apply a filtering to mainly only said transitions. In that case, the cut-off frequency chosen can be much smaller.
The current invention is not restricted to the use of low-pass or adaptive filters to flatten out said transitions. To be precise, all methods to realize such a flattening fall within the scope of this invention.
Based on the signal E is whether or not crossing a specific threshold value g, an automatic detection can be carried out at the locations 25 wherein the products to be rejected 3 are located.
Instead of generating signals D and E, according to the invention, an automatic detection can be carried out at those locations 17 wherein the products to be rejected are located, based on whether or not the signal A crosses a threshold value g, by merely analyzing said crossing in those zones wherein the products 2,3 are located according to signal C.
The signals A, A′, B, C, D, E are synchronized with each other. After all, these signals originate from the concentrated light beams 45, scanning the product stream in temporal movement. Every immediate value of one of these signals can therefore be correlated to the corresponding immediate value of the other signals. This synchronization allows applying one signal to another signal or combining both, because at every single moment the signals are coming from the same scanned position. In
To actually remove the products 3, air valves 11 are opened so that, at the locations where these products 3 were detected, each such product 3 will be blown out of the product stream.
The operation of the reject system 11 is carried out by comparing control signals generated by the signals D, E, to one or more threshold values gi. These control signals only contain information about either the product to be rejected 3, if this has to removed, or the product 2 to be accepted, if it has to be withheld.
This method according to the current invention is, of course, not restricted to the use of two detection units. In the case of more than two detection units, the corresponding signals 42 can for instance be algebraically combined to abovementioned signals A and B.
In an advantageous embodiment of the current invention, the zone 49, in which the background signal is located, is defined on various signals B, to be precise on all the output signals 39 of all the present detection units 44. The final Boolean signal C that determines where the background 19 is located and where the products 2,3 are located, is obtained by performing a logical-OR operation to all the separate signals C that are obtained according to the abovementioned method.
In an alternative embodiment, the output signals A, A′ of two detection units 44,44′ are combined in a two-dimensional graph. Both signals A, A′ originate from the same position in the product stream, but can differ in one or more signal parameters, so that different optical properties of the scanned position at that moment can be analyzed. These signals A, A′ can be obtained by filtering them out of a same detected light signal using spatial and/or frequency filters. Every point in this graph corresponds to a specific intensity level according to the path of the first signal A, combined with a specific intensity level according to the path of the second signal A′ at a specific moment in time, or, in other words, for a known immediate position of the concentrated scanning light beam 45. Specific signal combinations can occur several times if products 2,3 with the same optical properties are being scanned or every time the background element 5 is being scanned. By keeping these statistics, a two dimensional histogram can be created. Additionally, a color can be attributed to every histogram value. By attributing, for example, blue to the lowest value and gradually move up to red per rising value, a two-dimensional intensity map 55 can be created. On this map 55 contours of equal intensity can be drawn. As shown in
Every point in the two-dimensional diagram of
That way, in this perception, the zone 51 is being defined, in which the products to be accepted 2 are located, and the zone 52, in which the products to be rejected 3 are located. The zone 50, determined by the respective threshold values tmax, tmin and t′max, t′min, is represented by a square in said intensity map 55 containing the background as is illustrated in
In a graphical user interface one can, by means of a simple operation as is illustrated in
In a very advantageous embodiment the zones 50, 51 and 52 can be automatically calculated by means of known clustering algorithms, for example K-means.
The invention is not restricted to one and two-dimensional presentations, but can be easily extended to three and more dimensional presentations, be it by means of one, two or three-dimensional projections in those cases.
Hereafter a detailed description is given, as displayed in
The structure 26 is furthermore equipped with 2 inspection devices 9, 10. These inspection devices 9, 10 inspect an inspection zone 28 by means of a concentrated light beam that sweeps across the entire width W of the product stream. In the absence of products a background element is scanned that, according to the invention, may hold the optical characteristics of the products to be rejected.
The products 3 to be rejected are blown out of the product stream via the air valves. The accepted products 2 are guided through a shaft 53 towards possible further production steps.
During linear scanning of the product stream and the background element 5 signals are detected originating from this background element 5 and the product stream, notably the good products 2 and bad products 3. By adjusting frequency and spatial filters one can generate control signals from the detected signals that enable to sort the supplied products according to previously stipulated criteria using the reject system 11. Depending on the chosen background element 5 the background signal 47 will have a higher or lower intensity value: a white background gives a higher value, a black background gives a lower value as indicated in
In some cases, however, it is possible that a bad product 3′ generates a signal 48′ from which the peak is smaller than the signal 46 originating from a good product 2. This issue has already been clarified in the embodiment illustrated by
One could identify such bad products 3′ by defining a second, negative threshold value g2. The second threshold value g2 is chosen in such a way that the signal peaks 46 of the good products 2 would reach past this second threshold value g2, whereas the signal peaks 48′ of such bad products 3′ would not reach past the second threshold value g2, as indicated by the hatched area in
By a suitable choice of the threshold values g1 and g2, one can identify from the combined signal as indicated in
The selection method in the current state of the art as presented in
The good products are indeed situated in the strip between a first, negative threshold value g1 and a second, negative threshold value g2. One could sort the good products using this procedure by well selecting the values. The problem with the background however is not resolved: this is, as illustrated by
In the current state of the art this problem is solved by physically constructing the background element 5 in such a way that it provides a signal 47 that is comparable, for the detected optical parameter, to the signal 46 originating from a good product 2 and is thus situated within the strip constituted by both threshold values g1, g2. As mentioned above, it is, however, difficult to construct a background element 5 in such a way that, for the measured optical parameter(s), it not only resembles the actual good product 2 sufficiently well, but that it can retain this resemblance of a specific product 2 to a sufficient extent and over a considerable time. Furthermore the problem remains that one has to install for each product 2 a matching background element 5.
In the different embodiments of the invention the reference level 70 of the combined signal B is shifted using signal processing techniques to a new value 71 that preferably matches the signal level 46 of a good product 2. The signal peaks 48, 48′ of the bad products 3,3′ are being referenced in the processed signal D to the new reference level 71. To clarify the invention this new reference 71 is adjusted to the signal level 46 of a good product 2. This is illustrated in
Now one can identify the good products 2 by defining an appropriate threshold value(s) for the new signal D, as demonstrated in
The signal levels 46 of the good products 2 may show small variations, provided that these variations are situated around the reference level 71 within both threshold values g1, g2. The reject system is not activated in that case.
By appropriately choosing the threshold values g1 and g2, one can identify from a combined signal as indicated in
By shifting the reference level 70 to a suitable new value 71 one can better distinguish between the different products 2, 3 and/or 3′ and avoid the unnecessary activation of the reject system 11 either when detecting the background signal 47 and/or when a lower limit g2 is passed by a signal 46.
Because one shifts the reference level 70 of the background 47 to a new level 71 in the embodiments according to the invention using signal processing techniques, one picks a background signal 47 that differs , preferably considerably, from any product signal 46, 48, 48′. As one shifts the background reference level 47 via signal processing, preferably to the signal level 46 of a good product 2, the accurate value of this background level 47 is not important, as long as the background element 5 provides a signal 47 that differs, preferably considerably, from the signals 46, 48, 48′ of any product 2, 3, 3′. This choice of background signal 47 enables to clearly distinguish between the original reference level 70 and the product signals 46, 48, 48′ and, as such, refer these product signals to the new level 71.
In the state of the art, there are different ways to determine the level 70 of this background signal 47. One can allow the inspection configuration(s) 9,10 to work without supplying any products. The selected signal B will substantially match the signal 47 of the background element 5. One can also insert known products 2, 3, and/or 3′ at known positions in the scanning beam of the inspection unit 10. The immediate signal being detected, i.e. on the given moment t(s), matches a given immediate position of the scanning beam of light and thus with a given position x(mm) in the product stream. In this way one can identify and correlate the different signals 47, 46, 48 and/or 48′ in the signal B with the background element 5 and with the transported products 2, 3 and/or 3′. Instead of the above static tuning procedure, one can also proceed in a more flexible way. As illustrated in
As indicated in the previous paragraphs, the invention aims at redefining 71 the reference level 70 of the detected signal B via signal processing in such a way that a new signal D is obtained that permits the products 2, 3 and/or 3′ to be distinguished from each other without the problems present in the state of the art. Preferably the signal 46 coming from the good products 2 and the signal 47 coming from the background element 5 will be shifted to a substantially equal signal level 71, at least for the detected optical parameter.
In order to determine which zone of the signal B corresponds to the background signal 47 and, therefore, in which zone one should replace the signal level 70 by a new suitable reference level 71 for the product signals 46,48 and 48′, one can determine in the original signal B which zones 46,48 and 48′ indicate the presence of the products 2, 3, 3′ in the line scan and which zones 47 indicate the absence of a product or, in other words, the presence of the background element 5 in the line scan.
There are different embodiments to obtain a signal C based on one or more detected signals, of which the pulses are indicative of the location of a product 2, 3, 3′. This location signal C thus contains information about both the desired products 2 and the undesired products 3, 3′.
a-d illustrate a first embodiment. In the detected signal B one can distinguish zones corresponding to the background signal 47 from the zones corresponding to product signals 46, 48 and 48′. As stipulated above, because the signal 47 originating from the background element 5 is chosen in such a way that it differs from the signals 46, 48 and 48′ of the products 2, 3, 3′, one can define one or more threshold values g3 and g4 in the signal B, such that the signal levels 46, 48 and 48′ from the products 2, 3, 3′ are located outside these threshold values, e.g. on one side of this threshold value g3 and the signal level 47 of the background element 5 is located within these threshold values, e.g. on the other side of this threshold value g3.
In this embodiment the same detected signal B is first used to generate a product location signal C, after that, as shown above, this detected signal B is combined with the signal C to shift the reference level as illustrated in
a-d give a schematic representation of different embodiments of this signal processing process. In the embodiment illustrated in
As discussed in the previous sections it is not required for the signals C and B to originate from the same detected signals B.
As illustrated in
a-c illustrate another embodiment to obtain the product location signal C. In the embodiment illustrated by
In the embodiment of
An advantage of the embodiment illustrated by
a and 3b illustrate different embodiments of such a background element 5 that is capable of detecting uninterrupted light beams 34.
As illustrated in
A method described in the previous paragraphs through the combination of a number of the above-described features is the method for sorting a stream of products 2,3 in products to be accepted 2 and products to be rejected 3 comprising the steps of:
In the above embodiment, the location signal is preferably obtained by detecting the light that is falling directly on the background element and thus passes by the products 2,3, i.e. the light that is not blocked by products 2,3, as described above in relation to
In the latter embodiment, instead of generating signals D and E, an automatic detection is carried out at those locations where the products to be rejected are located, based on whether or not the signal A crosses a threshold value, by merely analyzing said crossing in those zones where the products 2,3 are located according to the location signal C.
The invention is then equally related to an apparatus for sorting products according to the method of the latter embodiment, said apparatus comprising:
According to a specific embodiment of the method of the invention, the method of obtaining the location signal illustrated in
According to the latter embodiment, the method comprises the steps of:
In the latter embodiment, the image may be taken by any suitable camera system, such as for example a system described in WO2008/116924A2, incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| BE 2006/0606 | Dec 2006 | BE | national |
This application is a continuation-in-part of U.S. application Ser. No. 12/518,239, tho which priority is claimed, submitted on Jun. 8, 2009, which is a U.S. national phase entry of PCT Application PCT/IB2007/055414, filed on Dec. 10, 2007, which claims priority to Belgian Application 2006/0606, filed on Dec. 8, 2006. U.S. application Ser. No. 12/518,239, PCT Application PCT/IB2007/055414, and Belgian Application 2006/0606 are hereby incorporated in their entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12518239 | Dec 2009 | US |
| Child | 13491342 | US |
