DK147835B

DK147835B - ELECTRO-OPTICAL ARRANGEMENT FOR THE DETECTION OF OBJECTS ON A TRANSPORT TAPE

Info

Publication number: DK147835B
Application number: DK495679A
Authority: DK
Inventors: Alain Rene Binet
Original assignee: Tissmetal Lionel Dupont
Priority date: 1978-11-27
Filing date: 1979-11-22
Publication date: 1984-12-17
Also published as: DK147835C; DK495679A; EP0012076A1; DE2963955D1; EP0012076B1

Description

i 147835in 147835

Opfindelsen angår et elektro-optisk arrangement til detektering af genstande på et transportbånd og omfattende en fotoelektrisk celle af refleksskanderingstype og en til cellen tilknyttet, reflekterende flade.The invention relates to an electro-optical arrangement for detecting objects on a conveyor belt and comprising a reflex scanning type photoelectric cell and a reflecting surface attached to the cell.

5 Specielt i forbindelse med postsorteringsanlæg er det kendt, at der er behov for at kunne detektere genstande. I det pågældende område ligger den største vanskelighed i, at de genstand, der transporteres på transportbåndet og skal sorteres, er af vidt forskellig 10 størrelse og ofte har meget uregelmæssig form.5 Especially in connection with mail sorting plants, it is known that there is a need to detect objects. In the area in question, the main difficulty lies in the fact that the items conveyed on the conveyor belt and which must be sorted are of very different sizes and often have very irregular shape.

Fig.l viser et kendt arrangement til detektering af genstande. På transportbåndet 1 findes der tre genstande, A, B og C. Genstanden A har form som en bro, hvorfor dens detektering via en konventionel foto-elek-15 trisk celle med sender 4 og modtager 4a fører til, at der i stedet for et enkelt signal opstår to signaler ved at lysbundtet afbrydes af den forreste del og af den bageste del af genstanden. Dette bevirker, at sorteringsanlæggets EDB-styring forstyrres af forviklingen mellem en 20 enkelt genstand og to elektriske signaler, som den forbipasserende genstand fremkalder, og som EDB-styringen opfatter som hørende til to genstande.Fig. 1 shows a known arrangement for detecting objects. On the conveyor belt 1, there are three objects, A, B and C. The object A is in the form of a bridge, and therefore its detection via a conventional photoelectric cell with transmitter 4 and receiver 4a results in a a single signal produces two signals by interrupting the light bundle by the front part and by the rear part of the object. This causes the sorting system's computer control to be disturbed by the interplay between a single object and two electrical signals that the passing object elicits and which the computer control perceives as belonging to two objects.

Den samme ulempe opstår for pakken B, som har en etiket, hvorved en konventionel detektor kommer til at 25 detektere to genstande, til trods for at der i realiteten kun er én enkelt genstand, der transporteres.The same disadvantage occurs for the package B, which has a label whereby a conventional detector will detect two objects, despite the fact that only a single object is transported.

Hvis der er en tynd genstand, såsom et brev C, kan det ske at denne genstand passerer udetekteret under lysbundtet, hvorved ovennævnte ulempe igen gør sig gældende.If there is a thin object, such as a letter C, it may happen that this object passes undetected under the light bundle, whereby the above disadvantage again applies.

30 Man kender også celler, såkaldte skanderingsceller, hvor lysbundtet vedvarende bibringes en sinus-agtig afbøjning. Disse celler er af den reflekterende type, hvilket indebærer, at der må placeres overfor sender-modtageren en spejlreflekterende flade, således at genstandene pas-35 serer mellem cellen og reflektoren. I et anlæg med transportbånd må cellen i praksis placeres langs kanten af båndet, medens reflektoren placeres på den anden side af båndet, eftersom en anden opstilling ville gøre det nød- 147835 2 vendigt i længderetningen at dele båndet i to dele, for at bundtet altid kan ramme reflektoren. Problemet med tynde genstande eller genstande med uregelmæssig overflade løses dog ikke herved, idet detekteringen i nærheden af 5 selve båndet er mangelfuld.30 Also known are cells, so-called scanning cells, where the light bundle is continuously imparted to a sinusoidal deflection. These cells are of the reflective type, which means that a mirror-reflecting surface must be placed opposite the transmitter-receiver so that the objects pass between the cell and the reflector. In a conveyor belt system, the cell must in practice be placed along the edge of the band while the reflector is placed on the other side of the band, since a different arrangement would make it necessary to divide the band lengthwise into two parts, so that the bundle always can hit the reflector. However, the problem of thin or irregular surface objects is not solved as the detection in the vicinity of the band itself is defective.

Opfindelsen tager sigte på at afhjælpe disse ulemper, og med henblik herpå er et elektro-optisk arrangement ifølge opfindelsen ejendommeligt ved, at den reflekterende flade er delt op i mindst to dele, der er 10 beliggende på hver sin side af genstandenes bane og set fra cellen fremtræder som en kontinuerlig flade.The invention aims to overcome these disadvantages, and for this purpose an electro-optical arrangement according to the invention is characterized in that the reflecting surface is divided into at least two parts, which are located on each side of the path of the objects and viewed from the side. the cell appears as a continuous surface.

Herved opnås på mekanisk enkel og driftssikker måde den fordel, at en passende placering af de reflekterende fladedele bringer cellen i stand til at "se" en 15 ubrudt flade, når båndet er tomt, hvorved justeringen af fotocellearrangementet forenkles, og at selv flade eller tynde genstande sikkert detekteres.In this way, the advantage is obtained in a mechanically simple and reliable way that an appropriate placement of the reflective surface parts allows the cell to "see" a continuous surface when the band is empty, thereby simplifying the adjustment of the photocell arrangement and even flat or thin. objects are safely detected.

Opfindelsen angår også et elektro-optisk arrangement til detektering af genstande på et transportbånd 20 og omfattende en fotocellesamling med en i hovedsagen lodret rsikke fotocelleenheder, der afgiver et lystæppe, samt en reflekterende flade, der er beliggende modsat cellen i forhold til transportbåndet, hvilket arrangement ifølge opfindelsen er ejendommeligt ved, at den re-25 flekterende flade er delt i mindst to plane dele beliggende på hver sin side af transportbåndet, idet overkanten af den del af nævnte flade, der er placeret ved cellen, ligger på højde med oversiden af transportbåndet, hvorhos refleksionskoefficienterne for de to dele 30 er indbyrdes forskellige, idet refleksionsfaktoren for den del, der befinder sig ved den modstående side af båndet, er større end refleksionsfaktoren for den del, der befinder sig foran transportbåndet.The invention also relates to an electro-optic arrangement for detecting objects on a conveyor belt 20 and comprising a photocell assembly having a generally vertically spherical photocell assembly emitting a light blanket, and a reflecting surface located opposite the cell relative to the conveyor belt, which arrangement The invention is characterized in that the reflecting surface is divided into at least two planar portions located on either side of the conveyor belt, the upper edge of said portion of said surface located at the cell being level with the upper surface of the conveyor belt. , wherein the reflection coefficients of the two parts 30 are mutually different, the reflection factor of the part located on the opposite side of the belt being greater than the reflection factor of the part located in front of the conveyor belt.

Fordelen herved er, at dette arrangement ingen 35 yderligere mekanisk justering kræver.The advantage of this is that this arrangement requires no further mechanical adjustment.

3 1478353 147835

Opfindelsen forklares nærmere i det følgende under henvisning til den skematiske tegning, hvor fig. 1 viser et kendt detekteringsarrangement, fig. 2 en udførelsesform for arrangementet ifølge 5 opfindelsen, og med en i hovedsagen konkav reflekterende flade, fig. 3 en anden udførelsesform med en plan reflekterende flade, fig. 4 en yderligere udførelsesform med fotocelle 10 af reflekstype med lystæppe, og fig. 5-7 diverse opstillinger af delene af den reflekterende flade.The invention is explained in more detail below with reference to the schematic drawing, in which fig. 1 shows a known detection arrangement; FIG. 2 shows an embodiment of the arrangement according to the invention and with a substantially concave reflecting surface; FIG. 3 shows another embodiment with a flat reflecting surface; FIG. 4 shows a further embodiment with light blanket photocell 10, and FIG. 5-7 miscellaneous arrangements of the parts of the reflecting surface.

Det i fig. 2 viste arrangement omfatter et transportbånd 1, der kører over valser 3, som er drejelige 15 om aksler 2, samt en skanderingscelle 4 af reflekstypen, f.eks. af den art, der i handelen findes under mærket JAY type MAD, hvilken celle er placeret ved venstre kant af båndet, samt en reflekterende flade 5, der er placeret ved højre kant af båndet. I overensstem-20 melse med opfindelsen udgøres foto-cellens reflektor dels af den reflekterende flade 5, der har form som en del af en cylinderflade, dels af en plan flade 6 beliggende ved cellen. Ved en præcis positionering af overkanten af den plane flade 6 er det muligt at opnå, at 25 lysbundtet forplanter sig langs overfladen af transportbåndet, således at en tynd genstand C, f.eks. et brev, sikkert detekteres. I praksis vil man i henhold til opfindelsen erstatte en vanskelig justering af de elektriske egenskaber for skandering i cellen med en 30 meget enklere mekanisk justering af beliggenheden af de reflekterende flader, der udgør reflektoren. Denne positionering kan iøvrigt finde sted ved hjælp af cellen, eftersom man blot progressivt skal løfte reflektoren 6, indtil båndet ikke lasngere ses under celleskanderingen.The FIG. 2 includes a conveyor belt 1 running over rollers 3 pivotable about shafts 2, and a reflex type scanning cell 4, e.g. of the kind commercially available under the JAY type MAD mark, which cell is located at the left edge of the band, as well as a reflective surface 5 located at the right edge of the band. In accordance with the invention, the reflector of the photocell is formed partly by the reflecting surface 5, which is shaped as part of a cylinder surface, and partly by a flat surface 6 located at the cell. By precisely positioning the upper edge of the planar surface 6, it is possible to achieve that the light bundle propagates along the surface of the conveyor belt, such that a thin object C, e.g. a letter, surely detected. In practice, according to the invention, a difficult adjustment of the electrical properties of scanning in the cell will be replaced by a much simpler mechanical adjustment of the location of the reflecting surfaces constituting the reflector. This positioning can also take place by means of the cell, since one only has to progressively lift the reflector 6 until the band is not loosened during the cell scan.

35 Det skal iøvrigt bemærkes, at cellen kun ser en kontinuerlig reflekterende flade.35 It should also be noted that the cell only sees a continuous reflecting surface.

147835 4147835 4

Det krumme spejl kan være til gene i et anlæg, der fungerer under vanskelige forhold, og under hensyn til det forhold, at det vigtigste ved et arrangement til detektering af genstande, er det der sker i nærheden af 5 båndet, kan man også anvende det detekteringsarrangement, der er vist i fig.3. Her består reflektoren af tre plane dele, 5, 6 og 7. I praksis danner fladerne 6 og 7 et vindue, der skanderes af det lysbundt, som reflekteres fra fladen 5, i det tilfælde hvor lysbundtet ikke er afbrudt, 10 og vender tilbage til cellen 4. I såfald vil en genstand, der forneden har form som en bro, detekteres som én enkelt genstand.The curved mirror can be a nuisance in a system that operates in difficult conditions, and considering that the most important thing in an object detection arrangement is that which happens near the band, it can also be used. detection arrangement shown in Fig.3. Here, the reflector consists of three planar parts, 5, 6 and 7. In practice, the surfaces 6 and 7 form a window that is scanned by the light beam reflected from the surface 5, in the case where the light beam is not interrupted, 10 and returns to cell 4. In this case, an object having the shape of a bridge below will be detected as a single object.

Når der er tale om en celle, der damer et lystappe,som vist i fig.4, er detekteringsmetoden nøjagtigt den samme, og 15 man genfinder i fig.4 en todelt reflektor 5 og 6 en række foto-celler, der udgør cellen 4 og har samme funktion som den skanderingscelle, der er vist i fig.2 og 3.In the case of a cell that dams a lightstick, as shown in Fig. 4, the detection method is exactly the same, and in Fig. 4, a two-part reflector 5 and 6 finds a series of photo cells that make up the cell 4. and has the same function as the scanning cell shown in Figs. 2 and 3.

Arrangementet ifølge opfindelsen giver mulighed for ved en enkel mekanisk justering at sikre en pålide-20 Hg detektering af genstande med uregelmæssig kontur. I visse tilfælde kan der være en slags mætning af foto-dioden ved overgang fra en del af den reflekterende flade til en anden del, hvilken mætning formentlig skyldes en for stor variation af lysstyrken i det reflekterede 25 bundt. Denne mætning af foto-dioden kommer til udtryk ved tilstedeværelsen af en død zone, hvori der ikke kan tilvejebringes betydningsfuld information. Det viser sig imidlertid, at denne døde zone næsten eksakt svarer til overfladen på transportbåndet, dvs. den mest interessan-50 te zone. I henhold til endnu en udførelsesform for opfindelsen kan refleksionsfaktoren på den del, der er beliggende bag båndet, være større end refleksionsfaktoren for den del, der befinder sig ved siden af cellen. Det er kendt, at refleksionsfaktoren eksempelvis kan udtryk-55 kes ved en multiplikationsfaktor for lysstyrken på en hvid flade under en vinkel på en trediedel grad. Herved vil lysstyrkerne i de reflekterede bundter til cellen 5 147835 være af samme størrelsesorden, og mætningen i den modtagende foto-diode ophøre.The arrangement according to the invention allows for a simple mechanical adjustment to ensure a reliable 20 Hg detection of irregular contour objects. In some cases, there may be some kind of saturation of the photo diode upon transition from one part of the reflecting surface to another, which saturation is probably due to an excessive variation of the brightness of the reflected beam. This saturation of the photo diode is expressed by the presence of a dead zone in which no significant information can be provided. However, it turns out that this dead zone corresponds almost exactly to the surface of the conveyor belt, ie. the most interesting-50 tea zone. According to yet another embodiment of the invention, the reflection factor of the portion located behind the band may be greater than the reflection factor of the portion located adjacent to the cell. It is known that, for example, the reflection factor can be expressed by a multiplication factor of the brightness of a white surface at an angle of a third degree. Hereby, the brightnesses of the reflected bundles of the cell 5 will be of the same order of magnitude and the saturation of the receiving photo diode will cease.

I den i fig.5 viste udførelsesform udgøres den reflekterende flade af to dele 5 og 6, hvoraf den ene i 5 hovedsagen er parabelformet. Som forklaret i det foregående skal refleksionsfaktoren på fladen 6 være mindre end på fladen 5. Med henblik herpå har fladen 6 en hældning på ca. 30° i forhold til vertikalen, idet man ved, at en flades refleksionsfaktor varierer med strålernes 10 indfaldsvinkel. Der er derfor ikke længere mætning af foto-dioden, eftersom de stråler, der reflekteres fra fladen 6, vender tilbage til cellen med en mindre lysstyrke end under normal indfaldsvinkel.In the embodiment shown in Fig. 5, the reflecting surface is constituted by two parts 5 and 6, one of which in the main case is parabolic. As explained above, the reflection factor on the surface 6 must be smaller than on the surface 5. For this purpose, the surface 6 has a slope of approx. 30 ° relative to the vertical, knowing that the reflection factor of a surface varies with the angle of incidence of the rays 10. Therefore, there is no longer saturation of the photo diode, since the rays reflected from the surface 6 return to the cell with a less brightness than below the normal angle of incidence.

I den i fig.6 viste udførelsesform er der taget 15 hensyn til det forhold, at lysbundtet fra cellen i praksis ikke udgår fra ét punkt, hvilket vil sige, at der ud fra en central plet findes en skyggezone. Ved at placere overkanten af reflektordelen 6 lidt under oversiden af transportbåndet 1, har man konstateret, at ovennævnte 20 mætningsfænomen ikke forekommer ved overgang fra en reflektordel til en anden.In the embodiment shown in Fig. 6, consideration is given to the fact that the beam of light from the cell does not in practice start from one point, which means that from a central spot a shadow zone exists. By placing the upper edge of the reflector portion 6 slightly below the upper surface of the conveyor belt 1, it has been found that the above saturation phenomenon does not occur upon transition from one reflector portion to another.

Fig.7 viser endnu en udførelsesform, som karakteriseres ved, at man har ændret den reflekterende flades refleksionsegenskaber, således at refleksionsfaktoren i de 25 dele, der befinder sig nærmest cellen, er mindre end i den modsatte del. Dette resultat kan nemt opnås ved at dække ovennævnte flader med en reflekterende film. Eksempelvis bliver der opnået tilfredsstillende resultater ved at dække delen 5 med en reflekterende beklædning 30 5a af typen "SCOTCHLITE 3870", medens delene 6 og 7 dækkes med en beklædning 6a, 7a af typen "SCOTCHLITE 3270", idet refleksionsfaktoren for "SCOTCHLITE 3270" er på 200, medens den er på 500 for "SCOTCHLITE 3870".Fig. 7 shows yet another embodiment, characterized in that the reflection properties of the reflecting surface have been altered, so that the reflection factor in the 25 parts closest to the cell is smaller than in the opposite part. This result can easily be achieved by covering the above surfaces with a reflective film. For example, satisfactory results are obtained by covering part 5 with a reflective covering 30 5a of the type "SCOTCHLITE 3870", while the parts 6 and 7 are covered with a covering 6a, 7a of the type "SCOTCHLITE 3270", the reflection factor of "SCOTCHLITE 3270" is at 200 while it is at 500 for "SCOTCHLITE 3870".

Det bemærkes, at "SCOTCHLITE" er varemærke for firmaet 35 3M. Naturligvis kan denne beklædning benyttes uanset, om den del, der befinder sig nærmest cellen, består af to reflektorer eller ej. Sidstnævnte udførelsesformIt should be noted that "SCOTCHLITE" is a trademark of the company 35 3M. Of course, this garment can be used regardless of whether or not the part closest to the cell consists of two reflectors. The latter embodiment

Claims

147835 has the advantage over the previous two that it does not require further mechanical adjustment. According to yet another embodiment shown in the drawing, the top edge of the part 6 of the reflecting surface can be saw-shaped and shaped so that there is little overlap with the lower edge of the part 5 of the reflecting surface. This causes the reflection zone factor to progressively vary between part 6 and part 5 of the reflecting surface, thereby alleviating the aforementioned phenomenon of saturation of the receiving photo diode. It should be noted that, for example, garments of different colors can be used.

An electro-optical arrangement for detecting objects (C, B, E) on a conveyor belt (1) and comprising a reflex scanning type photoelectric cell (4) and a reflecting surface associated with the cell, characterized in that the reflecting surface 20 is divided into at least two parts (5,6) located on either side of the path of the objects (C, B, E) and seen from the cell (4) as a continuous surface.

Arrangement according to claim 1, characterized in that the part (5) of the reflecting surface 25 which lies on the opposite side of the cell (4) of the conveyor belt (1) is constituted by a curved mirror.

Arrangement according to claim 1, characterized in that the reflecting surface is constituted by three planar parts (5,6,7), two parts (6,7) being located on the same side of the conveyor belt as the cell (4), while the third portion (5) is located on the opposite side of the conveyor belt (1), wherein the two first portions (6,7) define a scan window.

Arrangement according to one or more of claims 35 1-3, characterized in that the reflection factor for the part (5) located opposite the cell (4) is greater than for the part (s) (6,7) which is adjacent to the cell (4).