COUNTING DEVICE FOR THE REMOTE COUNTING OF STACKED OBJECTS IN A STACK OF THIN OBJECTS, AS WELL AS A COUNTING METHOD USING A COUNTING DEVICE

Abstract: A counting device detects intensity differences in reflections coming from stacked thin objects and possesses a radiation source (11) generating a radiation beam (12), photoelectric detection means (13) detecting the intensity differences in the radiation reflected by the objects and is provided with optical means (15-17) placed between said objects and the photoelectric detection means. The optical means comprise a diaphragm (15) having a diaphragm opening which in relation to the dimension of the beam of reflected radiation reaching the diaphragm, is smaller (pinhole).

Description: Counting device for -he remote counting of stacked objects la a stack of this objects, as well as a counting Method using a counting device ZΛυet invention relates to a counting device for tLe remote counting of stacked objec s in a. S ack c-i thin, ob- jectε euch as carton sheets, comprising a radiation source for the generation of a. radiation bean, means for moving -he radiation beam along the transverse edges cf the Stacked objects, photoelectric detection means for the detection of the intensity differences in radiation reflected, by the irradiated stacked objects, ss well as optical means placed between said stacked objects and said photoelectric detection -neans. A counting device α£ the abov -mentioned kind for counting a stack of corrugated board is known from the Dutch patent specifica ion Ho. 367, 30 as well &β from the ITS patent specification 3.581.067, referred tσ therein. The latter patent specification, reports that during the vertical scanning of the εtack tjie charges in reflec¬ tion behaviour occurring between tae separate layers are counted, it is rhe changes in b igh-neβe caused by the edge characteristics of the layers oi ma-erial which iollow in quick succession, that are counted, while slow changes in the nean trightneβs of the material are ignored. The Caster hc izαntal scanning periodically applied serves to deter- τr_ine the leaa brightness over a larger horizontal vidth. To count the corrugated boards, the scanning light beans are directed αntα the end face of the stack at an angle in order to obtain a mean brightness value which iβ indepen¬ dent of whether or not tje light beam happens to fall π the front σf a carton. Ωa disadvantage of this me ho is that a slight change in brightness between the adjacent. layers will cause faulty counting. The reason for there being so little change in brightness between adjacent lay¬ ers may be that the material edges have generally poor reflection properties, or tha.t fclie gap betveen the in. them¬ selves evenly reflecting layers, is too narrow. Hfcec count- iπg the corrugated hoards by the kαcv;α wetiled, it is alss possib-e that a split etween tw-= base sheets is counted as a. layer. "rt»e counting device described in the above-men ioned Dutch patent spedific ion l€T.550 uβeε a nethod it which a prede-endued width of one end at the stack is at the sane tiir.Ξ scanned in a faster horizontal πovenea by means cf a photoelec ric sensor consisting of a horizontal groj of ptotodiodsβ being- βwitched throug electric impulses alte - cately fcox one to the other end of the βensor, the irrαulβeε obtained are identified s coxing from a flat, base plare when a series of connected iapclses are detected, or from a corrugated plate of the corrugated board vhen a βeriee cf impulse groups is defected, αr aβ coning from a split becween adjacent corrugated boards when αo signal is detected, an by neanø cf a counting and reading device ich is set at a base plate or zero detection so that a shee of cartcn ia counted if a certain ncuber of itαpulεe groups coaling froir. the corrugated board ie detected, rhe device used tα carry out the above method is characterized in that elements are present for the provision of a narrow Illuminated scanning 2cne of predetermined length, a grcu oi pho odi das absorbing light reflec ed from the scanning zone and elemen s for succeε&ivs excitation of the pbczodiodes, a base plate detector comprising a counter STti zin a si nal t/hsπ a predetermined number of impulses generated by the photodiodes is counted, and in addition that a corrugated board detector is provided. Ths grcu? of photo icdea ma/ comprise cr instance 64 μhotodiodes. Another possibility applied in the known art involves the observance of the entire aza.dk by neanβ of a c o camera, with a subsequent aiiaJyzation of the picture conten . The diead a t ge of the nethad using the τr.cn. T ing sen- βor is the complex ccixtruction of the mechanical part of the device, while the diaadvβntage σf the method using a CCD camera is the relatively high coat of the CCD canera and the processing unit as well as the poor resolution- It will be clear from the a σve that counting stacks of carton or stacks of otaer thin αbjecte is technically not simple. Tie main reason or this is the relatively Blight contrast between -he reflection rrcir -he core and the reflection from ths sides of the stacked objects vhen the counting device is not just °j*ed for counting βhεe-s of corrugated board, but xn particular also for βolid carton, sheets cf plastic foil and the luce, (diere there are ew or no openings in and/or between hβ sheets. In practice, the great variations in distancs which often exist between the counting device and e staskβ of objects to be counted also play a role because of the variations in sheet βise wi h the stacfcβ baing ncr«d on an aligned path along a fixed device. lo avoid constantly having to move the coun - ing device or e 3tacks cf caxtcn it iβ deei a le to pro¬ vide a counting device with a great focal decta. The defi¬ cient focal depth of the device of the k own ar~ hae resulted in an increasingly complex counting device and in ths addition of extra Tα mec-J E which increase the mechanic coπplexity cf the device. It is -he object of the invention to provide a device of the kind nentiσned in ^.he preamble w ic may be mechanically simple and which result6 in a greater focal depth and ia characterized in that said optic Means corn- pxiae a diaphragm having a diaphragm opening, whica dia¬ phragm opening. In relation to the dirransionβ of tae beam of reflected radiation in the part oi said radiation path between said optical neana and said photoelectric detection mea s, is smaller. Surprisingly., even though, t* addition of ths diaphragx blocks cff a βignifiσanc amount α the reflection of the already αparae light, the result* LB a narked improveme of the counting device, rtiia is the effect of the greatly improved focal depth of tJaβ σour.tir.g device. T e presence of the diaphragm creates a very stria.. radi nio spot by means of which intensity differences can h- observed with s. better resclution than previously. It La also an advantage that a diaphragm, in particular a dia- phragm whose opening is aoc variable, is a simple element which is usually not expensive. In practice an embodiment of the invention was of interest vbich HΛB characterized in that said diaphragm has a diaphragm opening ranging from 0.1 an to 10 μci. It is further advancβgeous if this embodiment ia characterized in that said diameter ranges from 0.25 m to 2 μm . The importance of this mill be explained bslσw. A øinple embodiment of the invention is obtained with an enbodiπent characterised in that said photoelectric detection means comprises a single pl-jo oelectric cell. Phis embodiment contributes- tc the technical simplification of he device , A further important contribution tc improve the focal depth of the optical s s em of the device according to the invention can be realized by applying a preferred embodiment which is characterized in that aaid optical πeaas comprise a lens system whose focal distance ranges from 4 toσi to 5C mm, and is preferably about 55 mm. Surprisingly, placing a lane, which for this purpose has a short focal distance, n the bean of reflected radi¬ ation in front of the diaphragm., promotes the device's desirable geat increase in foc l dep-h. λ further contribution may be provided by applying an embediment which is characterized in that the radiation βocrcs is a monochromatic light source, such as a laser. An embodiment of the invention suitable fox station¬ ary mounting and which can for instance be used for counting staclced objects such as separate sheets of carton in a stack of carton, is characterized in that the device is provided with a catacable mirror to i ke tie radiation beam move aa a scanning beam over a certain scanning area. and the s ct of objects can. be placed within said scanning area so that the ob eσtβ can be scanned by a moving radi- a.ion. s o produced by the- roeving scanning beam. an important; consideration with Y-.e last-mentioned embodiment is, that if the device is provided vitb a rota¬ ting mirror, an extra difference in optical path length occurs because the distance between the counting device and the cop and .-xsttom of the stack is grearer then the dis¬ tance between the middle of the stack and the counting device, me improveirβαr of the focal depth., which is the achi«vett.ent of the invention, hβrefcre greatly contributes -o making the acvantageouε embodiment possible, in which the only wαvab-e part is tile rotating mirror. " ae invention not only relates to a counting device oi the kind mentioned in the preamble but alec to a methed for counting a number of cbjects, in particular separate 0 sheets of carton contained in a stack of carton, comprising the β_ep& of: genera ing a radia ion beam by means of a radiation scurce, moving the radiation beax in -he f rn of a scanning e m over a particular scann ng area., placing fcάe objects within said scanning area such that a moving E radiation spot produced by the moving s anning beam period¬ ically ccana the objects, absorbing ths radiation coning from the scanning spot and reflected by the ob ects, direc¬ ting ths reflected radiation via a radiation path provide with optical means -a photoelectric raeats and converting 0 the detected intensity differences in reflected radiation and absorbed by the pho oelectric xβans into an electric βigr-sl wh-ict ^s modulated by the intensity differences and muactifying the modulated signal, which quantification rep¬ resents the number of scanned objects. RJB alrsady en- Ε ticned, up tc now the known methods involved complex and expensive devices while, in addition, the resolving pewer was not always entirely satisfactory. To this end the method according to the invention offers a solution and is characterized in that said radiation source, said optical 0 me ns and said photoelectric means are ∞uπ ed βtationarily, the objects are rought vithin che scanning area, said scanning beam is noved by nβaaa of a mcvsble optical means, said reflected radiation in said rsdia iocn pate, is partially blocXed off by a diaphragm provided with 5 a ά-aphrags. opening, only the part at reflec ea radiation pass ng through the diaphragm opening is directed at said phctcelectric ireans, and said part of the refleered radi¬ ation is directed at only one single photoelectric cell pertainirg to the pho oelect ic ir.eaas. 18532 In the method according t the invention «. statioa&rily τr.αunted device iε used possessing a great fecal depth and a great resolving power. This allows good counting using a sim le apparatus while, moreover, the positioning of the stacks cf carton cr other objects to be counted is aot very critical. With respect to the simplicity of the device used and ales with respect to ths counting device's sensitivity to intensity differencen, an embodiment oi the method is cf consequence ccu ch is characterised in that the movable optical means is positioned in said radiation pa-h of the reflected radiation, and that, the reflected radiation absorbed by the photoelectric cell reaches the photoelec¬ tric cel via said πovable opti al means . The inventicn will now be further explained with leferen a to the schematic drawing illustrating, merely as non-limiting example, sone embodiments of the invent.ion, in tthic.: Pig. 1 6hows a longitudinal cross-section of counting device acccxrding to the invention standing on a floor in vertical position; Fig. 2 shows a view of a counting device of the kind shovn in Pig. on another scale, standing on a floor next to a pallet loaded with carton; a d Fig. 3 shows s βiπil≤.r croaa-section as Fig. 1 αf an embodiment having a vertically translatery optical/elec¬ tronical unit. The counting device 1 shown in the drawing serves for ths electronic detection of differences in intensity. In the schematic embodiment a α>wn, the counting device com¬ prises a housing 2 which is in principle closed having a top vail 5, a floor 4, a rsax wall 5, a front wall a, and side vails 7, of wλieh only one ie shown in the drawing. l . the front wall a window 9 is provided which ay be closed by sa s of, for instance, a glass pane 9. The whole is built solid and dustproof r suitable for use in an indus¬ trial environment. The cσuΛtir. device may be firmly posi¬ tioned vertically on a factory floor id and, if desired, xay be fixed thereto by suitable meane (not sho n'' . Inside je housing 2 a radiation scarce 11 [shown very schematically) a provided for the ger ration of a radiation beam of sufficient intensity. The radiation beam is represented by the central line 12. Za addition co the radiation source for the generation, of the radiation beam, :JIE device is provided with photoelectric detection means, schematically indicated at 13, which serve to detect inten¬ sity differences in the radiation reflected by objects irradiated by the radiation bean. The reflerted radiation is rerpresented Ln the drawin by the reflected radiation beam's central line 14. The figures IE. 16 and 17 refer to optical means placed in the radiation path cf said cbject. in this case the stack of cerεon 4, aui the photoelsc ric detection means 13. The optical ir ane 15 consists cf a diaphragn bavir-c a diaphragm opening is, which diaphragm opening, in rela¬ tion to the dimensions of the beam 14 of reflscted radi¬ ation in he part of said radiation path between the optical means 15-17 and the photoelectric detection means 13, is smallex. The other optical xβana crx riβe a lens system 16 atd a rotating mirror 17. In the drawing the lens system lβ ris shown schematically and may comprise one or xcre lens elementB for the concentration at reflected radi¬ ation onto thvβ diaphragm 15. The rotating mirror l"? to:n~ prises a bilaterally reflecting mirror element 19 as well as a driving motor 2Tt whose rotation axis is positioned at right angles to the plane of the dracrisg. The mirror element 19 is rctatβd in the direct-on represented by the arrow 21 by means of the xotor 20 at a velocity of P for example, 4 rota ionβ per second. lbs rotating mirror Vt prcvideβ the radiation beam 12 with a βcanning πκ>rve e.π.t which is at least suitable for ecanning a stack of carton 4. AS shown in ?ig. 2, the radiation beam 1 thus oveβ in vertical direction at least between two extreme positions L2a and 12.3 including a scanting angle a. The diaphragm 15 is a small hole, a so-called •pin- hole*, having a diaphragm opening of between C .1 μn. and 10 t-sι. Practice has shown that a pre±ered range of iixcπslαπε lies between ύ.25 μn and 2. 0 μia. The photoelectric detec- 97/18532 8 tior. means 13 comprise only one single photoelectric cell, the focal distance of the lens system 1£ ranges from 4 ma to 5a ran, being preferably 25 mm. The effect of using a lens system having a ehort focal distance and a diaphragm having a email opening is that a pixel-li e element is cre¬ ated cm the photoelectric cell 13. facilitat nc the percep¬ tion of intensity differences vaith a high resolution. Due to the fact that the lens has a short focal distance, the high resolution is accompanied by a great cal depth. Ihanke b tile hich resolution, objects of little thickness such as sheets of solid carton or paper can be counted. For αnntinc eclid carton a diaphragm opening of 2 μm. as sed. For counting uhe thinner duplex carton, 1 μr. is used and £=r counting paper. C.25 μm is used. The radiation source 11 may, for instance , bs pro¬ vided by a monochromatic light source suc as a laser. Lasers are particularly suitable for the generation of monochrsmatic light in a narrow, concentrated beam and for this reason they are particularly euitable for the present 0 device. The radiation beam 12 ie moved in the fo m of scan¬ ning ray over t e scanning area, a- by means cf rotating mirror 17. Iτia stack of carton 4 xay be placed with little precision on an ordinary pallet 22 within said scanning area, to allow the end face of the separate sheets cf car- 5 ton 4.1. 4.2. ...., 4.π to be scanned by a movable light spot (not shown in the drawing) produced by the movable scanning beam 2. The photoelectric cell 13 is coupled (in a iraaαer not shewn* with electronic evaluation means (not shown, but 0 Known in themselves which are suitable for the conversion oi detected intensity d fferenceε in the reflected radi¬ ation absorbed by the photoelectric cell into an electric signal modulated by the intensity differences and quantify¬ ing the nodulated electric signal, which quantification Ξ represents the number of scanned objects, being in this case the number of scanned sheets of carton 4.1, 4.2, ..... 4.n. The rotating ntrrαr 17 is alβo used to direct the reflected radiation 14 at the lens system 16 and thus ulti¬ mately at the diaphragm 15 and h pho oelectric cell 13. Although .Pigs, l a d 2 only show a single embodiment of the invention, other embodiments axe also possible v thl the scope of the invention as defined by the claims. Dspendlrg an the operation conditions, other optical σompo- nente may be added. For icsLance a second lens may be uβed in the -βπs system far the coiliiMtior at: the reflected beam. In principle other suitable radiation sources may also be used apart from a laser, for instance, a suitable light source. Furthe r as shown in Pig. 3, the use of a rotating mirror way be left out and instead, the entire Optics1/elec ronic unit cαπtprisicg the radiation source 2 '- , the Le system 16, the diaphragm 15 and the photodetectcr 13, together mounted onto a support element 22, may be cved vertically up and down. Xc this end the housing 22 cαxprises two bars 24 as parallel guide links. A xctor 25 drives the support element in a usual manner, wfcich is not detailed liβre. A vertical wall of the housing 23 is pro¬ vided with a slot 25 to allsvr the emitted and reflected light beams 12 and li respectively, to pass through.

Claims: 8532 10 ΓTΛTMΛ 1. A counting device ilj iox the remote counting of stacked objects in a stack of thin cbjecta such as carton sheets, comprising a radiation scurce (11) for the gener- s.ticn of a radiation be93 (12/, xeaπβ for -roving the radi¬ ation beam £12) along the tranεverse edges of ths stacked objects, photoelectric detec ea meane (13) for the detection cf fcae intensity i ferences in radiation (14) reflected by the irradiated stacked objects i4) , aa veil aβ cptic&l means (15-17) placed between said stacked objects and said photoelectric detection, meets, characterised in that eaid optic means (15-17) αo przse a diaphragm (151 having a diaphragn opening lζ. \ , whicla diaphragm opening.. in relation tα the dimensions of the beam (14) of reflected radiation in the part of 3aid radiation path between said optical means (15-17) and said photoelectric detection means il2 ) , is smaller. i. A counting device according to claim . charac¬ terised in that said diaphracx. (151 has a diaphragn opening fl&l ranging from C.l inn ro 10 μm. 3. A σounting device according to claim 2. charac¬ terised in chat εaid diameter ranges from o.ΞS μn. to 2 μm. 4. A counting device according to claim 1. charac¬ terised in that said photoelectric detection means {131 comprise oαe single photoelectric cell. 5. counting device according to claim 1, charac¬ terised in that said optical means [L5-l7 ' ι corr riβe a lens syeteπ (16] whose focal distance ranges iron 4 mm to So mm, and is preferably about 25 mm. 6. A. counting device according to any one o: the preceding claims, characterisad in that the radiation source (11 is a monochroαu.cic light source, s ch as a laser. 7. λ. counting device according tc any one Df the preceding claims, characterized in. that - - e counting device is pro idsd with a rotatahle πirror (171 to sake tie radiation, beex C12I move as a scan¬ ning beam over * certain Ecannir-c; area (at , and - the objects (4.1, 4.2. ..., 4. a, can be placed 5 withir. said scanning axea [a) oo that the objects can be βcanted by a moving radiation spot produced by ti moving scann ng beam. s. A. metnod f csuπting s number of objects, in particular tbe number of objects contained in a stack (4) , Id such as tbe number of separate sheets or carton (4.1, 4.2, ..., 4.n) contained in a stack of carton, comprising the steps of: - generating a radiation bean (12] ley neans of a radiation source (11J, IS - moving the radiation bean (12; in the fcnr. of a scanning beam over a certain scannlt-c araa <er; , - lacing tbe objects 14.l, 4.2, ... r 4.π) within said scanning area suc that a moving radiation spot pro¬ duced by the moving scanning beam periodically scans the 20 objects, - abβorhtion of ths radiation '14) cciring frotii the seaming spot and reflected by the objects, - directing the reflected radiation via a radiat on pa ti provided with optical means [15-17) to photoelectric 25 means tl3} and converting che detected intensity eϋii-Br- encea in reflected radiation and absorbed by c e photoelec¬ tric means into an electric signal which ia modulated, by the intensity di ferences, - and quantifying ths modulated signal, which guan- 30 tification represents the number of scanned objects [4.1, 4.2 4.n.ι , characterized in that - aald radiation source (lij .. said optical ensaas (15-17] and said photoelectric neans CJJ are mounted 35 statiαnarily, - ths objects (4.1, 4.2 4.n) are brc gjit with¬ in the scanning area ia) , - said scanning beam is moved by means of a movable optical ne&ns [19), O 97/18532 12 - said reflected radia ion (14] in said radiation path {15-17) s partially blocked off by a diaphragm (151 provided vLzii a diaphragm opening (IB], - cnly the part of reflected radiation (14) pausing E through the diaphragm opening ilfl; is directed at said pho¬ toelectric neacs (131, and - said part of the reElected radiation is directed at only one single photoelectric cell (L3t pertaining tc the photoelectric means. ID 9. A method according to claim ". characterised in that - the movable optical means tis) is placed in sals radiation path (15-1 * ?: of the reflected radiation (14) sad - the reflected radiaticn (14) absorbed by- tbe pho- 1S toelectric cell reaches che photoelectric cell (13) via said movable optical ireanβ (19) .

Inventors: VAN OOSTEROM WILLEM, VAN OOSTEROM, WILLEM
Applicants: FUNCTION CONTROL RESEARCH B V, OOSTEROM WILLEM VAN, FUNCTION CONTROL RESEARCH B.V., VAN OOSTEROM, WILLEM
Application year: 1996
Main classification: G06M9
IPC codes: G06M1, G06M9