EP0377006A1 - Method and device for reading a bar code on a substantially motionless medium - Google Patents

Method and device for reading a bar code on a substantially motionless medium

Info

Publication number
EP0377006A1
EP0377006A1 EP89905708A EP89905708A EP0377006A1 EP 0377006 A1 EP0377006 A1 EP 0377006A1 EP 89905708 A EP89905708 A EP 89905708A EP 89905708 A EP89905708 A EP 89905708A EP 0377006 A1 EP0377006 A1 EP 0377006A1
Authority
EP
European Patent Office
Prior art keywords
support
lines
scanning
peaks
amplitude
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89905708A
Other languages
German (de)
French (fr)
Inventor
Michel Gustave Jules Fardeau
Denis Pierre Bâtiment B EUZENNE
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Bertin Technologies SAS
Original Assignee
Bertin et Cie SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bertin et Cie SA filed Critical Bertin et Cie SA
Publication of EP0377006A1 publication Critical patent/EP0377006A1/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10544—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum
    • G06K7/10821—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices
    • G06K7/10861—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices sensing of data fields affixed to objects or articles, e.g. coded labels
    • G06K7/10871—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices sensing of data fields affixed to objects or articles, e.g. coded labels randomly oriented data-fields, code-marks therefore, e.g. concentric circles-code
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07C—POSTAL SORTING; SORTING INDIVIDUAL ARTICLES, OR BULK MATERIAL FIT TO BE SORTED PIECE-MEAL, e.g. BY PICKING
    • B07C3/00—Sorting according to destination
    • B07C3/10—Apparatus characterised by the means used for detection ofthe destination
    • B07C3/14—Apparatus characterised by the means used for detection ofthe destination using light-responsive detecting means
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10544—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum
    • G06K7/10821—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices
    • G06K7/1092—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation by scanning of the records by radiation in the optical part of the electromagnetic spectrum further details of bar or optical code scanning devices sensing by means of TV-scanning

Definitions

  • the invention relates to a method and a device for reading a bar code on a substantially stationary support.
  • substantially stationary support is meant, in the present description, a support stationary or relatively slow moving relative to the 5. reading device.
  • Bar codes are now well known and applied in various fields: automatic sorting of mail, processing of bank checks, automatic identification, during checkout, of products sold in stores, etc. 10
  • the codes can be read by moving an optical pen over the label by hand or the product in front of a reading eye.
  • the surface to be read is very limited, and it is not necessary for the direction of movement to be strictly or even approximately perpendicular to the bars of the code, it suffices that it cuts all the bars.
  • the sticks typically have a height of 4 mm, a width of 0.4 mm and are separated from each other by distances equal to a step of 1.66 mm or a multiple of this step.
  • the "routing" codes occupy approximately 45 mm and include 0 twenty sticks divided into five groups each comprising a "start” stick and three sticks corresponding to a number between 0 and 9, in a code "3 among 5" (the three sticks occupying three positions out of five possible).
  • Postal envelopes carrying these bar codes scroll at high speed (for example 3 m / s) in front of a reading device which must identify the code precisely and extremely quickly.
  • the devices used for this are generally of the type described in French patent 2,441,889. They project a light beam (suitable for exciting the fluorescent material of the sticks), narrow and having a height of 20 to 30 mm, on the zone where the indexing codes scroll.
  • the light beam returned by the mailing scrolls is received by a photodetector associated with filters to be sensitive only to the fluorescence spectrum of the rods, and the amplitude peaks corresponding to the detection of the rods are recorded and processed by electronic means. and IT.
  • Reading an indexing code on the upper postal fold of a stack poses a certain number of problems which cannot be solved by known devices.
  • the invention particularly aims to solve this problem. It relates to a method and a device for reading a bar code on a substantially stationary support, which are applicable both to reading the indexing codes of postal objects and to that of the bar codes provided on the labels of products sold in stores, on checks and other documents. It also relates to a method and a device of this type, which are extremely precise.
  • the invention therefore provides a method of reading a bar code on a substantially stationary support, consisting in scanning at least a part of the surface of the support by means of a light beam, in receiving on a photodetector the beam returned by the surface of the support, to detect the 10 variations in amplitude of the signal produced by the photodetector and to record the peaks of these variations as well as their positions to deduce the structure of the bar code, characterized in that it consists in scanning the surface of the support along a grid of lines, by displacement of the substantially punctual impact of a light beam along lines which are substantially parallel to the same predetermined fixed direction, and which follow one another at a predetermined interval, to be detected for each scanning line the peaks of amplitude of the photodetector signal, and to make a cumulative of the amplitudes of the peaks of concordant positions in lines su ccessives, to identify the position and possibly the type of each bar of the code and to differentiate it from any parasitic signals.
  • the pitch between the successive scan lines is of course less than the height of an index code stick, so that several scan lines can cut the same stick, even if they are oriented obliquely with respect to with sticks.
  • a step of 0.5 mm proves to be entirely suitable for reading the postal letter indexing codes. 35 . p ar
  • the scanning speed is preferably constant, which makes it possible to identify the positions of amplitude peaks per a counting time.
  • the area to be scanned can be of the same order of magnitude as that of a postal envelope. It can for example be fixed at 20 x 25 cm, which corresponds substantially to the dimensions of the means for receiving and transporting stacks of postal envelopes at the outlet of automatic sorting machines.
  • the duration of scanning of such a surface is between a few tenths of a second and about one second, and is therefore entirely acceptable.
  • the cumulation of the amplitudes of the corresponding position peaks on successive scanning lines makes it possible to reconstruct images of rods or of code bars, similar to those which are obtained in the device described in the aforementioned French patent, applicable to the reading of codes indexing on fast moving media. It is therefore immediately understood that the computer processing process of the corresponding signals may be substantially the same in both cases, which avoids costly investments.
  • the method also consists in compensating for the offsets of the amplitude peaks from one line to the next, when the scanning lines intersect obliquely the bars of the code, in order to reconstruct amplitude peaks aligned with each other on lines perpendicular to the scan lines. This brings us back to the case where the scanning lines are exactly perpendicular to the direction of the code bars.
  • the method consists in locating on each scanning line a point of known fixed position, and in moving relative to this point the amplitude peaks located on this line, by a distance function of the angle of the scanning lines relative to the bars of the code, to align these peaks, perpendicular to the line, with the amplitude peaks of matching positions of the neighboring or adjacent lines. Compensation of the above-mentioned offset of the amplitude peaks from one line to the next is therefore very simple, when the scanning lines are oriented obliquely with respect to the bars of the code. In addition, passing through this fixed point of known position makes it possible to initialize the time counting, for determining the positions of the amplitude peaks.
  • the dimension, in a direction perpendicular to the scanning lines, of the impact of the light beam on the surface of the support is of the same order of magnitude as the pitch of the scanning lines.
  • the shape of the point of impact of the light beam on the support can be circular or else elongated in a direction parallel to the bars of the code.
  • the method also consists, for carrying out the scanning in successive lines parallel to the surface of the support, to mount pivotally about an axis substantially parallel to the surface of the support an optical assembly comprising at minus a mirror for returning the light beam to the surface of the support.
  • This pivoting optical assembly may also include the photodetector and the optical means for receiving the light beam returned by the surface of the support.
  • the displacement of the point of impact of the light beam on a line of the surface of the support can be produced by the rotation of a polygonal mirror, interposed between a light source and a reflecting mirror towards the surface of the support.
  • the invention also provides a device for reading a bar code on a substantially stationary support, intended in particular for the execution of the method described in the above, and comprising a light source, optical means for projecting a beam light coming from the source on the surface of the support, means for transmitting the beam returned by the surface of the support, photodetector means for receiving the returned beam, and means for processing the signals produced by the photodetector means, characterized in that '' it comprises optical means for moving the point of impact of the light beam on the surface of the support in a frame of successive lines substantially parallel to a predetermined fixed direction, succeeding each other at a predetermined interval and in that the processing means of signals include means for recording the amplitude peaks of the signals corresponding to the different line s scanning, and means for accumulating the amplitudes of the peaks of concordant position in successive lines.
  • this device also comprises means for locating a fixed point of known position on each scanning line, such as for example an optical fiber, one end of which is placed in the path of the beam of sweep and whose other end is associated with a photodetector.
  • the device comprises an optical assembly mounted pivoting about an axis parallel to the surface of the support and comprising at least one mirror for returning the light beam to the surface of the support, and optionally the means for transmission of the beam returned by the support surface and the aforementioned photodetector means.
  • electric motors are provided for driving the optical assembly in rotation about the aforementioned axis and for driving a rotating polygonal mirror, interposed between a light source and a mirror for returning the light beam to the surface of the support.
  • FIG. 1 schematically represents a postal envelope comprising a indexing code
  • FIG. 2 schematically represents part of a conveyor belt with compartments for receiving stacks of postal envelopes
  • FIG. 3 schematically represents, on a larger scale, scan lines over part of an indexing code
  • FIG. 4 schematically represents the series of electrical signals obtained at the output of a photodetector
  • FIG. 5 represents these series of signals after compensation for their offset
  • FIG. 6 schematically represents the transposed image of the sticks of code which correspond to the alignments of amplitude peaks of the signals of FIG. 5;
  • FIG. 7 schematically represents a reading device according to the invention
  • FIG. 8 schematically represents the signal processing circuits associated with this device.
  • FIG. 1 where there is shown, to fix ideas, a postal envelope of a conventional type, called window envelope.
  • This envelope 10 therefore comprises a window 12 in which the name and address of the recipient appear, a stamp 14 or a postage mark in its upper right corner, as well as postmarks, and a indexing code 16 in the lower right corner.
  • This indexing code is formed by a series of fluorescent sticks printed on the envelope 10 and whose arrangement corresponds to the coded transcription of the postal code of the recipient's address.
  • the indexing code can include twenty rods 18 (routing code) and possibly nineteen additional rods (distribution code).
  • the scanning lines will most often be oblique with respect to the direction of the rods 18 of the code 16, as shown in FIG. 3. More specifically, the invention provides for compensating for the offset of the peaks, of amplitude of the signals from the photodetector, offset due to the obliquity of the scanning lines relative to the rods 18.
  • Each passage of the point of impact of the light beam on a rod 18 during the scanning results in the formation of an amplitude peak 24 in the signal produced by the photodetector.
  • the amplitude peaks 24 corresponding to the same rod 18 are offset from one scanning line to the other, as shown in FIG. 4. This offset is compensated in the following way: we can first of all observe its existence when, from one scanning line to another, two amplitude peaks 24 are offset by a relatively small distance.
  • the offset will be equal to the step multiplied by the sine of 30 °, or about 0.25 mm.
  • This very small offset cannot be confused with the distance normally separating the amplitude peaks of two consecutive sticks, which is 1.66 mm. The observation of such an offset therefore necessarily indicates, when it is repeated from one scanning line to another, an obliquity of the scanning lines relative to the direction of the rods.
  • a correlation can be established between the arrangement of the signals in FIG. 5 and the arrangement of the rods in FIG. 6, by making a sum or a sum of the amplitudes ⁇ of the transversely aligned peaks detected on successive scanning lines.
  • the sum of the amplitudes of the peaks relating to the same rod will correspond substantially to the amplitude of a signal produced by a photodetector receiving the image of a stick in accordance with the technique described in the aforementioned prior French patent, all other things being equal.
  • the detection of the rods represented in FIG. 6 by the prior device, and the detection of the rods represented in FIG. 3 by the device according to the invention will produce signals of the same type, which can be processed in a similar manner .
  • FIG. 7 schematically represents a reading device according to the invention.
  • This device comprises a light source 28, such as an argon laser, a quartz or iodine lamp and an associated filter or also a semiconductor laser and frequency doubler assembly.
  • the cylindrical light beam 30 produced by this source is returned, by a mirror 32, to a polygonal mirror 34 rotatably mounted about an axis 36 parallel to the surface of the letter 10 to sweep.
  • the polygonal mirror 34 is in fact an annular mirror with plane facets 38 having an angle at the center of 10 ° for example, which corresponds to a number of facets equal to 36 for the mirror 34, and to a deflection of the beam of 20 ° .
  • the light beam 30 is reflected by each facet 38 on a mirror 40 of very small area which returns it to the envelope 10 to be scanned.
  • the mirror 34 is driven in rotation about the axis 36 in the direction indicated by the arrow, so that the light beam is initially reflected as indicated between 30, and finally in 30 proceedings, traversing a scanning line L between these two positions.
  • the light beam reflected by the surface of the envelope 10 is recovered by a lens 42 with a large field and a large depth of field, so much as to form an image of the scanning line L on the input window 44 of an anamorphoser 46, in particular of the fiber optic type, which transforms the image of the scanning line L into a circular surface adapted to the input window of a photodetector 48. Possibly, an objective?
  • the optical assembly comprising the deflection mirror 32, the rotary polygon mirror 34, the deflection mirror 40, the objective 42, the anamorphoser 46, the optics 50, the filter 52 and the photodetector 48, is carried by a plate mounted for rotation about a transverse pivot axis 54 which is parallel to the surface of the envelope 10 and perpendicular to the axis 36 cited above. If one wishes to avoid driving the light source 28 in rotation, the axis 54 can be substantially aligned with the axis of the light beam 30 at the output of the source 28.
  • This device according to the invention also comprises, to determine on 0 each scanning line a reference point whose fixed position is known, an optical fiber 56, one end of which is placed in the path of the light beam 30, at the start of the scanning line and the other end of which is associated, for example by a lens 58, with the input window of a photodetector 60.
  • the passage of the light beam 30, over 5 the end of the fiber 56 will produce, by via the photodetector 60, a synchronization signal which can be considered as a reference point of known position on each scanning line.
  • a synchronization signal which can be considered as a reference point of known position on each scanning line.
  • the optical fiber 56, and possibly the objective 56 or the photodetector 60 will have to follow the rotational movement around the axis
  • 10 is 0.5 mm, 400 scanning lines with a length of 250 mm each are arrived at.
  • the corresponding scanning time is between a few tenths of a second and about one second.
  • FIG. 8 schematically represents the circuits for processing the signals produced by the photodetectors 48 and
  • the output of the photodetector 48 is connected by an amplifier 62 to a low-pass filter 64, the output of which is connected on the one hand to an analog-digital converter 66 and on the other hand to a differentiator 68 associated with a detection circuit 70 signal edges whose output is connected, on the one hand, to the analog-digital converter 66 and, on the other hand, to the input of a FIFO (Firt In-First Out) memory (multi-register with offset) 72 to another input to which the output of the analog-digital converter 66 is also connected.
  • FIFO Firt In-First Out
  • the photodetector 60 for locating a fixed point at the start of the scanning line is connected by a trigger circuit 74 on the one hand to a line number counter 76 and on the other hand to the reset input of a counter 78 controlled by a clock 80.
  • the outputs of the counters 76 to 78 are connected to inputs of the FIFO memory 72.
  • This this is associated with a microprocessor 82 connected to an interf ace of ⁇ communication 84 and controlling the servo circuits 86 and 88 of the electric motors 90 and 92 for driving the rotating polygonal mirror 34 and the optical assembly mounted in rotation about the axis 54.
  • circuits operate from the generally as follows:
  • the variations in amplitude of the signal produced by the photodetector 48 are processed by the amplifier 62 and the low-pass filter 64 then are digitized by the converter 66 before being recorded in the memory 72.
  • the differentiator 68 associated with circuit 70 for detecting fronts makes it possible to differentiate the digitized signals corresponding to amplitude peaks of the photodetector signal and those corresponding to valleys between which amplitude peaks are located and trigger the converter 66.
  • the photodetector 60 makes it possible to count the scanning lines ⁇ via trigger 74 and counter 76 and reset counter 78 at the start of each scan line.
  • the clock 80 makes it possible to locate on each scanning line the position of the peaks and troughs of amplitude recorded in the memory 72.
  • the microprocessor 82 controls the motors 90 and 92 via the 0 circuits, of servo-control 86 and 88, then acquires in memory 72 the amplitudes? soon. batteries and dips of the signals from the photodetector 48, as well as their position, (numbers of the scanning lines and position of the peaks and dips in the scanning lines).
  • Software, stored in a memory associated with the microprocessor 82, 5 makes it possible to carry out the following treatments:
  • indexing code identify the structure of the indexing code, either from groups of three: information (position, sum of the amplitudes of the peaks and number of scan lines) or from groups of two information (position u of the amplitude peaks and amplitude of these peaks, weighted by the number of scan lines concerned).
  • One of the advantages of the invention is that the software suitable for carrying out this processing is very little different from the software associated with the method and the device described in the aforementioned prior French patent, so that - the person skilled in the art, for the implementation of the invention, will be satisfied with an adaptation of the known software.
  • the invention is applicable both to the reading and to the recognition of indexing codes appearing on postal envelopes, as bar codes appearing on labels of various objects or products, on checks, and other documents.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Artificial Intelligence (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
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Abstract

Procédé et dispositif pour détecter et identifier un code barre sur un support (10), par balayage de la surface du support (10) au moyen d'un faisceau lumineux dont le point d'impact décrit une trame de lignes successives (L1, L2, L3, L4, ...) parallèles à une direction fixe prédéterminée qui peut couper en oblique les barres (18) du code. L'invention permet de détecter et de reconnaître des codes barres sur des objets sensiblement immobiles.Method and device for detecting and identifying a bar code on a support (10), by scanning the surface of the support (10) by means of a light beam whose point of impact describes a frame of successive lines (L1, L2 , L3, L4, ...) parallel to a predetermined fixed direction which can cut obliquely the bars (18) of the code. The invention makes it possible to detect and recognize bar codes on substantially stationary objects.

Description

PROCEDE ET DISPOSITIF DE LECTURE READING METHOD AND DEVICE
D'UN CODE BARRES SUR UN SUPPORTOF A BAR CODE ON A MEDIUM
SENSIBLEMENT IMMOBILESUBSTANTIALLY IMMOBILE
L'invention concerne un procédé et un dispositif de lecture d'un code barres sur un support sensiblement immobile.The invention relates to a method and a device for reading a bar code on a substantially stationary support.
Par support sensiblement immobile, on entend, dans la présente description, un support immobile ou en déplacement relativement lent par rapport au 5. dispositif de lecture.By substantially stationary support is meant, in the present description, a support stationary or relatively slow moving relative to the 5. reading device.
Les codes barres sont maintenant bien connus et appliqués dans divers domaines : tri automatique du courrier, traitement des chèques bancaires, identification automatique, lors du passage aux caisses, de produits vendus en magasins, etc.. 10 Lorsque les barres du code ont une hauteur relativement importante (cas des étiquettes de produits), les codes peuvent être lus par déplacement à la main d'un stylo optique sur l'étiquette ou du produit devant un oeil de lecture. La surface à lire est très limitée, et il n'est pas nécessaire que la direction de déplacement soit rigoureusement ou même approximativement perpendicu- 5 laire aux barres du code, il suffit qu'elle coupe toutes les barres.Bar codes are now well known and applied in various fields: automatic sorting of mail, processing of bank checks, automatic identification, during checkout, of products sold in stores, etc. 10 When the code bars have a height relatively large (in the case of product labels), the codes can be read by moving an optical pen over the label by hand or the product in front of a reading eye. The surface to be read is very limited, and it is not necessary for the direction of movement to be strictly or even approximately perpendicular to the bars of the code, it suffices that it cuts all the bars.
Par contre, lorsque les barres du code sont de hauteur faible et que la longueur du code est relativement importante (codes barres des lettres et des chèques), il est indispensable que la direction de déplacement du code par rapport à un oeil de lecture soit sensiblement perpendiculaire aux barres 0 du code. Pour cette raison, on a été amené à faire défiler, à vitesse souvent élevée, les objets portant les codes à lire devant un oeil de lecture fixe et statique.On the other hand, when the code bars are of low height and the code length is relatively large (bar codes of letters and checks), it is essential that the direction of movement of the code relative to a reading eye is appreciably perpendicular to the 0 bars of the code. For this reason, we were led to scroll, often at high speed, the objects bearing the codes to be read in front of a fixed and static reading eye.
Les installations automatiques de tri postal fonctionnent sur ce principe. Un code barre appelé "indexation" en France et correspondant au code 5 postal de destination, est imprimé en bâtonnets fluorescents sur la face de l'enveloppe ou du paquet qui porte l'adresse. Les bâtonnets ont typiquement une hauteur de 4 mm, une largeur de 0,4 mm et sont séparés les uns des autres par des distances égales à un pas de 1,66 mm ou un multiple de ce pas. Les codes "acheminement" occupent environ 45 mm et comprennent 0 vingt bâtonnets répartis en cinq groupes comportant chacun un bâtonnet "start" et trois bâtonnets correspondant à un chiffre compris entre 0 et 9, dans un code "3 parmi 5" (les trois bâtonnets occupant trois positions parmi cinq possibles).Automatic postal sorting systems operate on this principle. A bar code called "indexing" in France and corresponding to the postal code 5 of destination, is printed in fluorescent sticks on the face of the envelope or package which bears the address. The sticks typically have a height of 4 mm, a width of 0.4 mm and are separated from each other by distances equal to a step of 1.66 mm or a multiple of this step. The "routing" codes occupy approximately 45 mm and include 0 twenty sticks divided into five groups each comprising a "start" stick and three sticks corresponding to a number between 0 and 9, in a code "3 among 5" (the three sticks occupying three positions out of five possible).
Les plis postaux portant ces codes barres défilent à vitesse élevée (par exemple 3 m/s) devant un dispositif de lecture qui doit identifier le code de façon précise et extrêmement rapide. Les dispositifs utilisés pour cela sont en général du type décrit dans le brevet français 2 441 889. Ils projettent un faisceau lumineux (propre à assurer l'excitation de la matière fluorescente des bâtonnets), étroit et ayant une hauteur de 20 à 30 mm, sur la zone où défilent les codes d'indexation. Le faisceau lumineux renvoyé par les plis postaux en défilement est reçu par un photodétecteur associé à des filtres pour être sensible uniquement au spectre de fluorescence des bâtonnets, et les pics d'amplitude correspondant à la détection des bâtonnets sont enregistrés et traités par des moyens électroniques et informatiques. Les résultats obtenus sont extrêmement bons, puisque le taux de rejet des plis postaux est inférieur à 2,5 pour 1000 en dépit des défauts d'impression des bâtonnets fluorescents formant les codes d'indexation. Il est apparu maintenant souhaitable de pouvoir lire ces codes, non seule¬ ment sur les plis postaux amenés à vitesse élevée à l'entrée des machines automatiques de tri, mais aussi sur les piles de plis postaux formées à la sortie de ces machines. Ces piles vont en effet constituer des liasses de plis postaux ayant une même destination, et une étiquette d'acheminement devra être imprimée et jointe à chaque liasse.Postal envelopes carrying these bar codes scroll at high speed (for example 3 m / s) in front of a reading device which must identify the code precisely and extremely quickly. The devices used for this are generally of the type described in French patent 2,441,889. They project a light beam (suitable for exciting the fluorescent material of the sticks), narrow and having a height of 20 to 30 mm, on the zone where the indexing codes scroll. The light beam returned by the mailing scrolls is received by a photodetector associated with filters to be sensitive only to the fluorescence spectrum of the rods, and the amplitude peaks corresponding to the detection of the rods are recorded and processed by electronic means. and IT. The results obtained are extremely good, since the rejection rate of postal items is less than 2.5 per 1000 despite the printing defects of the fluorescent sticks forming the indexing codes. It has now appeared desirable to be able to read these codes, not only on postal envelopes brought at high speed at the entrance to automatic sorting machines, but also on stacks of postal envelopes formed at the outlet of these machines. These stacks will indeed constitute bundles of postal envelopes having the same destination, and a routing label must be printed and attached to each bundle.
La lecture d'un code d'indexation sur le pli postal supérieur d'une pile pose un certain nombre de problèmes qui ne peuvent être résolus par les dispositifs connus.Reading an indexing code on the upper postal fold of a stack poses a certain number of problems which cannot be solved by known devices.
En effet, ces piles sont soit immobiles, soit en déplacement lent au moment de la lecture. Les parties des plis postaux portant les codes d'indexation occupent des positions différentes, et ont des orientations différentes, par rapport au dispositif de lecture. Paradoxalement, il est donc beaucoup plus difficile de lire le code d'indexa¬ tion d'un pli postal immobile, que celui d'un pli déplacé à grande vitesse. L'invention a notamment pour but de résoudre ce problème. Elle a pour objet un procédé et un dispositif de lecture d'un code barres sur un support sensiblement immobile, qui soient applicables aussi bien à la lecture des codes d'indexation des objets postaux qu'à celle des codes barres prévus sur les étiquettes de produits commercialisés en magasin, sur les chèques et sur d'autres documents. Elle a également pour objet un procédé et un dispositif de ce type, qui soient extrêmement précis.Indeed, these batteries are either stationary or moving slowly at the time of reading. The parts of the postal envelopes carrying the indexing codes occupy different positions, and have different orientations, relative to the reading device. Paradoxically, it is therefore much more difficult to read the indexing code of a stationary mail envelope, than that of a letter moved at high speed. The invention particularly aims to solve this problem. It relates to a method and a device for reading a bar code on a substantially stationary support, which are applicable both to reading the indexing codes of postal objects and to that of the bar codes provided on the labels of products sold in stores, on checks and other documents. It also relates to a method and a device of this type, which are extremely precise.
Elle a encore pour objet un procédé et un dispositif de ce type, qui soient relativement bon marché et dont la mise en oeuvre ne nécessite pas un 5 investissement extrêmement coûteux.It also relates to a method and a device of this type, which are relatively inexpensive and whose implementation does not require an extremely expensive investment.
L'invention propose donc un procédé de lecture d'un code barres sur un support sensiblement immobile, consistant à balayer au moins une partie de la surface du support au moyen d'un faisceau lumineux, à recevoir sur un photodétecteur le faisceau renvoyé par la surface du support, à détecter les 10 variations d'amplitude du signal produit par le photodétecteur et à enregis¬ trer les pics de ces variations ainsi que leurs positions pour en déduire la structure du code barres, caractérisé en ce qu'il consiste à balayer la surface du support selon une trame de lignes, par déplacement de l'impact sensiblement ponctuel d'un faisceau lumineux suivant des lignes qui sont 15 sensiblement parallèles à une même direction fixe prédéterminée, et qui se succèdent à un intervalle prédéterminé, à détecter pour chaque ligne de balayage les pics d'amplitude du signal du photodétecteur, et à faire un cumul des amplitudes des pics de positions concordantes dans des lignes successives, pour identifier la position et éventuellement le type de chaque 20 barre du code et pour la différencier d'éventuels signaux parasites.The invention therefore provides a method of reading a bar code on a substantially stationary support, consisting in scanning at least a part of the surface of the support by means of a light beam, in receiving on a photodetector the beam returned by the surface of the support, to detect the 10 variations in amplitude of the signal produced by the photodetector and to record the peaks of these variations as well as their positions to deduce the structure of the bar code, characterized in that it consists in scanning the surface of the support along a grid of lines, by displacement of the substantially punctual impact of a light beam along lines which are substantially parallel to the same predetermined fixed direction, and which follow one another at a predetermined interval, to be detected for each scanning line the peaks of amplitude of the photodetector signal, and to make a cumulative of the amplitudes of the peaks of concordant positions in lines su ccessives, to identify the position and possibly the type of each bar of the code and to differentiate it from any parasitic signals.
Il suffit donc, selon l'invention, de balayer tout ou partie de la surface du support par une trame de lignes successives parallèles à une direction fixe prédéterminée, qui de préférence est choisie de telle sorte que les lignes de balayage coupent les barres du code. 25 En effet, si la direction de balayage est sensiblement parallèle aux barres du code, le pas entre les lignes successives de balayage doit être très faible, ce qui conduit à des temps importants de balayage et à l'utilisation de cartes mémoire de très grande capacité.It is therefore sufficient, according to the invention, to sweep all or part of the surface of the support by a frame of successive lines parallel to a predetermined fixed direction, which preferably is chosen so that the scanning lines cut the bars of the code. . 25 In fact, if the scanning direction is substantially parallel to the code bars, the pitch between the successive scanning lines must be very small, which leads to significant scanning times and to the use of very large memory cards. capacity.
Le pas entre les lignes successives de balayage est bien entendu inférieur à 30 la hauteur d'un bâtonnet de code d'indexation, de façon à ce que plusieurs lignes de balayage puissent couper un même bâtonnet, même si elles sont orientées en oblique par rapport aux bâtonnets. Un pas de 0,5 mm se révèle par exemple tout à fait approprié à la lecture des codes d'indexation des plis postaux. 35. par ailleurs, la vitesse de balayage est de préférence constante, ce qui permet de repérer les positions des pics d'amplitude par un comptage de temps. La surface à balayer peut être du même ordre de grandeur que celle d'un pli postal. On peut par exemple la fixer à 20 x 25 cm , ce qui correspond sensiblement aux dimensions des moyens de réception et de transport de piles de plis postaux en sortie des machines automatiques de tri. La durée de balayage d'une telle surface est comprise entre quelques dizièmes de seconde et une seconde environ, et est donc tout à fait acceptable. Le cumul des amplitudes des pics de position correspondante sur des lignes successives de balayage permet de reconstituer des images de bâtonnets ou de barres de code, semblables à celles qui sont obtenues dans le dispositif décrit dans le brevet français précité, applicable à la lecture des codes d'indexation sur des supports en défilement rapide. On comprend donc immédiatement que le processus de traitement informatique des signaux correspondants pourra être sensiblement le même dans les deux cas, ce qui évite des investissements coûteux. Selon une autre caractéristique de l'invention, le procédé consiste également à compenser les décalages des pics d'amplitude d'une ligne à la suivante, lorsque les lignes de balayage coupent en oblique les barres du code, pour reconstituer des pics d'amplitude alignés entre eux sur des lignes perpendi¬ culaires aux lignes de balayage. On se ramène ainsi dans le cas où les lignes de balayage sont exactement perpendiculaires à la direction des barres du code.The pitch between the successive scan lines is of course less than the height of an index code stick, so that several scan lines can cut the same stick, even if they are oriented obliquely with respect to with sticks. A step of 0.5 mm, for example, proves to be entirely suitable for reading the postal letter indexing codes. 35 . p ar Moreover, the scanning speed is preferably constant, which makes it possible to identify the positions of amplitude peaks per a counting time. The area to be scanned can be of the same order of magnitude as that of a postal envelope. It can for example be fixed at 20 x 25 cm, which corresponds substantially to the dimensions of the means for receiving and transporting stacks of postal envelopes at the outlet of automatic sorting machines. The duration of scanning of such a surface is between a few tenths of a second and about one second, and is therefore entirely acceptable. The cumulation of the amplitudes of the corresponding position peaks on successive scanning lines makes it possible to reconstruct images of rods or of code bars, similar to those which are obtained in the device described in the aforementioned French patent, applicable to the reading of codes indexing on fast moving media. It is therefore immediately understood that the computer processing process of the corresponding signals may be substantially the same in both cases, which avoids costly investments. According to another characteristic of the invention, the method also consists in compensating for the offsets of the amplitude peaks from one line to the next, when the scanning lines intersect obliquely the bars of the code, in order to reconstruct amplitude peaks aligned with each other on lines perpendicular to the scan lines. This brings us back to the case where the scanning lines are exactly perpendicular to the direction of the code bars.
Selon encore une autre caractéristique de l'invention, le procédé consiste à repérer sur chaque ligne de balayage un point de position fixe connue, et à déplacer par rapport à ce point les pics d'amplitude se trouvant sur cette ligne, d'une distance fonction de l'angle des lignes de balayage par rapport aux barres du code, pour aligner ces pics, perpendiculairement à la ligne, avec les pics d'amplitude de positions concordantes des lignes voisines ou adjacentes. On réalise ainsi très simplement la compensation du décalage précité des pics d'amplitude d'une ligne à la suivante, lorsque les lignes de balayage sont orientées en oblique par rapport aux barres du code. En outre, le passage par ce point fixe de position connue permet d'initialiser le comptage de temps, pour la détermination des positions des pics d'amplitude. Avantageusement, la dimension, dans une direction perpendiculaire aux lignes de balayage, de l'impact du faisceau lumineux sur la surface du support est du même ordre de grandeur que le pas des lignes de balayage. De cette façon, lorsqu'on opère le cumul des amplitudes des pics de position concordante, on reconstitue à peu près l'image complète d'une barre du code.According to yet another characteristic of the invention, the method consists in locating on each scanning line a point of known fixed position, and in moving relative to this point the amplitude peaks located on this line, by a distance function of the angle of the scanning lines relative to the bars of the code, to align these peaks, perpendicular to the line, with the amplitude peaks of matching positions of the neighboring or adjacent lines. Compensation of the above-mentioned offset of the amplitude peaks from one line to the next is therefore very simple, when the scanning lines are oriented obliquely with respect to the bars of the code. In addition, passing through this fixed point of known position makes it possible to initialize the time counting, for determining the positions of the amplitude peaks. Advantageously, the dimension, in a direction perpendicular to the scanning lines, of the impact of the light beam on the surface of the support is of the same order of magnitude as the pitch of the scanning lines. In this way, when the cumulative amplitudes of the position peaks are operated concordant, we almost reconstruct the complete image of a code bar.
La forme du point d'impact du faisceau lumineux sur le support peut être circulaire ou bien allongée dans une direction parallèle aux barres du code. Selon un mode de réalisation préféré de l'invention, le procédé consiste également, pour réaliser le balayage en lignes successives parallèles de la surface du support, à monter pivotant autour d'un axe sensiblement parallèle à la surface du support un ensemble optique comprenant au moins un miroir de renvoi du faisceau lumineux vers la surface du support. Ainsi, par pivotement pas à pas du miroir de renvoi, on peut déplacer le faisceau lumineux d'une ligne de balayage à la suivante.The shape of the point of impact of the light beam on the support can be circular or else elongated in a direction parallel to the bars of the code. According to a preferred embodiment of the invention, the method also consists, for carrying out the scanning in successive lines parallel to the surface of the support, to mount pivotally about an axis substantially parallel to the surface of the support an optical assembly comprising at minus a mirror for returning the light beam to the surface of the support. Thus, by stepping the deflection mirror step by step, the light beam can be moved from one scanning line to the next.
Cet ensemble optique pivotant peut comprendre également le photodétec¬ teur et les moyens optiques de réception du faisceau lumineux renvoyé par la surface du support. Le déplacement du point d'impact du faisceau lumineux sur une ligne de la surface du support peut être produit par la rotation d'un miroir polygonal, interposé entre une source lumineuse et un miroir de renvoi vers la surface du support.This pivoting optical assembly may also include the photodetector and the optical means for receiving the light beam returned by the surface of the support. The displacement of the point of impact of the light beam on a line of the surface of the support can be produced by the rotation of a polygonal mirror, interposed between a light source and a reflecting mirror towards the surface of the support.
L'invention propose également un dispositif de lecture d'un code barres sur un support sensiblement immobile, destiné en particulier à l'exécution du procédé décrit dans ce qui précède, et comprenant une source lumineuse, des moyens optiques de projection d'un faisceau lumineux issu de la source sur la surface du support, des moyens de transmission du faisceau renvoyé par la surface du support, des moyens photodétecteurs de réception du faisceau renvoyé, et des moyens de traitement des signaux produits par les moyens photodétecteurs, caractérisé en ce qu'il comprend des moyens optiques pour déplacer le point d'impact du faisceau lumineux sur la surface du support selon une trame de lignes successives sensiblement parallèles à une direction fixe prédéterminée, se succédant à un intervalle prédéterminé et en ce que les moyens de traitement de signaux comprennent des moyens d'enregistrement des pics d'amplitude des signaux correspondant aux diffé¬ rentes lignes de balayage, et des moyens de cumul des amplitudes des pics de position concordante dans des lignes successives.The invention also provides a device for reading a bar code on a substantially stationary support, intended in particular for the execution of the method described in the above, and comprising a light source, optical means for projecting a beam light coming from the source on the surface of the support, means for transmitting the beam returned by the surface of the support, photodetector means for receiving the returned beam, and means for processing the signals produced by the photodetector means, characterized in that '' it comprises optical means for moving the point of impact of the light beam on the surface of the support in a frame of successive lines substantially parallel to a predetermined fixed direction, succeeding each other at a predetermined interval and in that the processing means of signals include means for recording the amplitude peaks of the signals corresponding to the different line s scanning, and means for accumulating the amplitudes of the peaks of concordant position in successive lines.
Selon une autre caractéristique de l'invention, ce dispositif comprend également des moyens de repérage d'un point fixe de position connue sur chaque ligne de balayage, tels par exemple qu'une fibre optique dont une extrémité est placée sur le trajet du faisceau de balayage et dont l'autre extrémité est associée à un photodétecteur.According to another characteristic of the invention, this device also comprises means for locating a fixed point of known position on each scanning line, such as for example an optical fiber, one end of which is placed in the path of the beam of sweep and whose other end is associated with a photodetector.
Grâce à ce repérage d'un point fixe de position connue sur chaque ligne de balayage, on peut commodément compenser, par le calcul, les décalages d'une ligne à l'autre des pics d'amplitude correspondant à la même barre de code coupée en oblique par les lignes de balayage.Thanks to this location of a fixed point of known position on each scan line, it is convenient to compensate, by calculation, the shifts from one line to another of the amplitude peaks corresponding to the same cut code bar obliquely by the scan lines.
Selon une autre caractéristique de l'invention, le dispositif comprend un ensemble optique monté pivotant autour d'un axe parallèle à la surface du support et comprenant au moins un miroir de renvoi du faisceau lumineux vers la surface du support, et éventuellement les moyens de transmission du faisceau renvoyé par la surface de support et les moyens photodétecteurs précités.According to another characteristic of the invention, the device comprises an optical assembly mounted pivoting about an axis parallel to the surface of the support and comprising at least one mirror for returning the light beam to the surface of the support, and optionally the means for transmission of the beam returned by the support surface and the aforementioned photodetector means.
De? moteurs électriques sont prévus pour l'entraînement de l'ensemble optique en rotation autour de l'axe précité et pour l'entraînement d'un miroir polygonal tournant, interposé entre une source lumineuse et un miroir de renvoi du faisceau lumineux vers la surface du support.Of? electric motors are provided for driving the optical assembly in rotation about the aforementioned axis and for driving a rotating polygonal mirror, interposed between a light source and a mirror for returning the light beam to the surface of the support.
De préférence, ces moteurs électriques sont commandés par un micropro¬ cesseur faisant partie des moyens précités de traitement de signaux. La source lumineuse utilisée, en particulier pour exciter la fluorescence des bâtonnets d'un code d'indexation sur un pli postal, peut être un laser à argon dont on conserve la raie à 488 nm, ou bien une lampe à quartz ou à arc, associée avec un filtre de sélection de la bande d'excitation de la fluores¬ cence ou encore un ensemble laser semi-conducteur et doubleur de fréquen¬ ce. L'invention sera mieux comprise, et d'autres détails, caractéristiques et avantages de celle-ci apparaîtront à la lecture de la description explicative qui suit, faite en référence aux dessins annexés dans lesquels : La figure 1 représente schématiquement un pli postal comprenant un code d'indexation ; La figure 2 représente schématiquement une partie d'une bande transporteu- se à compartiments de réception de piles de plis postaux ;Preferably, these electric motors are controlled by a microprocessor forming part of the aforementioned signal processing means. The light source used, in particular to excite the fluorescence of the sticks of an indexing code on a postal fold, can be an argon laser whose line is kept at 488 nm, or else a quartz or arc lamp, associated with a filter for selecting the excitation band for fluorescence or else a semiconductor laser and frequency doubler assembly. The invention will be better understood, and other details, characteristics and advantages thereof will appear on reading the explanatory description which follows, made with reference to the appended drawings in which: FIG. 1 schematically represents a postal envelope comprising a indexing code; FIG. 2 schematically represents part of a conveyor belt with compartments for receiving stacks of postal envelopes;
La figure 3 représente schématiquement, à plus grande échelle, des lignes de balayage sur une partie d'un code d'indexation ;FIG. 3 schematically represents, on a larger scale, scan lines over part of an indexing code;
La figure 4 représente schématiquement les séries de signaux électriques obtenus en sortie d'un photodétecteur ; La figure 5 représente ces séries de signaux après compensation de leur décalage ; La figure 6 représente schématiquement l'image transposée des bâtonnets de code qui correspondent aux alignements de pics d'amplitude des signaux de la figure 5 ;FIG. 4 schematically represents the series of electrical signals obtained at the output of a photodetector; FIG. 5 represents these series of signals after compensation for their offset; FIG. 6 schematically represents the transposed image of the sticks of code which correspond to the alignments of amplitude peaks of the signals of FIG. 5;
La figure 7 représente schématiquement un dispositif de lecture selon l'invention ; La figure 8 représente schématiquement les circuits de traitement de signaux associés à ce dispositif.FIG. 7 schematically represents a reading device according to the invention; FIG. 8 schematically represents the signal processing circuits associated with this device.
On se réfère tout d'abord à la figure 1 où l'on a représenté, pour fixer les idées, une enveloppe postale d'un type classique, dite enveloppe à fenêtre. Cette enveloppe 10 comprend donc une fenêtre 12 dans laquelle apparaissent le nom et l'adresse du destinataire, un timbre 14 ou une marque d'affranchis¬ sement postal dans son angle supérieur droit, ainsi que des cachets d'oblité¬ ration, et un code d'indexation 16 dans le coin inférieur droit. Ce code d'indexation est formé d'une série de bâtonnets fluorescents imprimés sur l'enveloppe 10 et dont l'agencement correspond à la transcrip- tion codée du code postal de l'adresse du destinataire. Le code d'indexation peut comprendre vingt bâtonnets 18 (code d'acheminement) et éventuelle¬ ment dix-neuf bâtonnets supplémentaires (code de distribution). Lorsque les enveloppes 10 défilent, à vitesse élevée, en étant positionnées et orientées toutes de la même façon, leurs codes d'indexation 16 peuvent être lus par un dispositif décrit dans le brevet français antérieur précité, ce dispositif permettant de commander une machine automatique de tri. Lorsque ce tri est réalisé, les lettres se retrouvent groupées par destinations et forment des piles plus ou moins hautes, dans des casiers prévus à la sortie de la machine de tri. Ces piles de lettres vont ensuite être formées en liasses, par exemple au moyen d'une feuille de matière plastique, à laquelle sera adjointe une étiquette indiquant la destination de la liasse. Pour l'impression automatique de ces étiquettes, il est nécessaire de lire automa¬ tiquement le code d'indexation qui a été porté sur l'enveloppe 10 se trouvant sur le dessus de chaque pile. Toutefois, comme ces piles sont immobiles, ou bien sont déplacées à vitesse lente sur une bande transporteuse 20 compre¬ nant des cloisons transversales 22 de taquage sur lesquelles les lettres sont en appui par un de leurs bords, et comme les lettres supérieures des piles peuvent prendre une orientation variable par rapport aux cloisons de taquage 22, comme représenté en figure 2, on comprend qu'il n'est pas possible d'utiliser le dispositif décrit dans le brevet antérieur pour lire les codes 16 d'indexation de ces enveloppes. Ce problème est résolu selon l'invention par un balayage fin de la surface de l'enveloppe 10 qui porte le code d'indexation 16, ce balayage étant réalisé par une trame de lignes successives Ll, L2, L3, etc.. parallèles à une direction fixe prédéterminée, qui est perpendiculaire aux bâtonnets 18 du code 16 lorsque la lettre 10 est correctement positionnée, par exemple en étant en appui sur une rive de taquage 22.We first refer to Figure 1 where there is shown, to fix ideas, a postal envelope of a conventional type, called window envelope. This envelope 10 therefore comprises a window 12 in which the name and address of the recipient appear, a stamp 14 or a postage mark in its upper right corner, as well as postmarks, and a indexing code 16 in the lower right corner. This indexing code is formed by a series of fluorescent sticks printed on the envelope 10 and whose arrangement corresponds to the coded transcription of the postal code of the recipient's address. The indexing code can include twenty rods 18 (routing code) and possibly nineteen additional rods (distribution code). When the envelopes 10 scroll, at high speed, while being positioned and oriented all in the same way, their indexing codes 16 can be read by a device described in the aforementioned prior French patent, this device making it possible to control an automatic machine for sorting. When this sorting is carried out, the letters are found grouped by destinations and form more or less tall stacks, in compartments provided at the outlet of the sorting machine. These stacks of letters will then be formed into bundles, for example by means of a plastic sheet, to which will be added a label indicating the destination of the bundle. For the automatic printing of these labels, it is necessary to automatically read the indexing code which has been carried on the envelope 10 located on the top of each stack. However, as these stacks are stationary, or else are moved at slow speed on a conveyor belt 20 comprising transverse jogging partitions 22 on which the letters are supported by one of their edges, and as the upper letters of the stacks can take a variable orientation relative to the jogging partitions 22, as shown in FIG. 2, it is understood that it is not possible to use the device described in the prior patent to read the codes 16 for indexing these envelopes. This problem is solved according to the invention by a fine scanning of the surface of the envelope 10 which carries the indexing code 16, this scanning being carried out by a frame of successive lines L1, L2, L3, etc. parallel to a predetermined fixed direction, which is perpendicular to the rods 18 of the code 16 when the letter 10 is correctly positioned, for example by being supported on a jogging edge 22.
Dans la pratique, selon l'orientation relative dans laquelle se présente la lettre supérieure, les lignes de balayage seront le plus souvent en oblique par rapport à la direction des bâtonnets 18 du code 16, comme représenté en figure 3. De façon plus spécifique, l'invention prévoit de compenser le décalage des pics, d'amplitude des signaux du photodétecteur, décalage dû à l'obliquité des lignes de balayage par rapport aux bâtonnets 18.In practice, depending on the relative orientation in which the upper letter appears, the scanning lines will most often be oblique with respect to the direction of the rods 18 of the code 16, as shown in FIG. 3. More specifically, the invention provides for compensating for the offset of the peaks, of amplitude of the signals from the photodetector, offset due to the obliquity of the scanning lines relative to the rods 18.
Chaque passage du point d'impact du faisceau lumineux sur un bâtonnet 18 au cours du balayage se traduit par la formation d'un pic d'amplitude 24 dans le signal produit par le photodétecteur. Les pics d'amplitude 24 correspon¬ dant à un même bâtonnet 18 sont décalés d'une ligne de balayage à l'autre, comme représenté en figure 4. Ce décalage est compensé de la façon suivante : on peut tout d'abord constater son existence lorsque, d'une ligne de balayage à l'autre, deux pics d'amplitude 24 sont décalés d'une distance relativement faible.Each passage of the point of impact of the light beam on a rod 18 during the scanning results in the formation of an amplitude peak 24 in the signal produced by the photodetector. The amplitude peaks 24 corresponding to the same rod 18 are offset from one scanning line to the other, as shown in FIG. 4. This offset is compensated in the following way: we can first of all observe its existence when, from one scanning line to another, two amplitude peaks 24 are offset by a relatively small distance.
En effet, pour un pas de 0,5 mm entre les lignes de balayage et pour un angle de 30° entre la direction des lignes de balayage et la perpendiculaire aux bâtonnets 18 du code, le décalage sera égal au pas multiplié par le sinus de 30°, soit environ 0,25 mm. Ce décalage très faible ne peut être confondu avec la distance séparant normalement les pics d'amplitude de deux bâton¬ nets consécutifs, qui est de 1,66 mm. La constatation d'un tel décalage indique donc nécessairement, lorsqu'elle se répète d'une ligne de balayage à l'autre, une obliquité des lignes de balayage par rapport à la direction des bâtonnets. Si l'on connaît la position d'un point fixe de référence sur chaque ligne de balayage, il est facile de compenser, par le calcul, le décalage précité en déplaçant la position de ce point de référence sur la ligne de balayage, d'une distance égale au décalage mais dans le sens contraire, et en procédant ainsi d'une ligne de balayage à la suivante.Indeed, for a step of 0.5 mm between the scanning lines and for an angle of 30 ° between the direction of the scanning lines and the perpendicular to the rods 18 of the code, the offset will be equal to the step multiplied by the sine of 30 °, or about 0.25 mm. This very small offset cannot be confused with the distance normally separating the amplitude peaks of two consecutive sticks, which is 1.66 mm. The observation of such an offset therefore necessarily indicates, when it is repeated from one scanning line to another, an obliquity of the scanning lines relative to the direction of the rods. If the position of a fixed reference point on each scan line is known, it is easy to compensate, by calculation, for the above-mentioned offset by moving the position of this reference point on the scan line, by a distance equal to the offset but in the opposite direction, and thus proceeding from one scan line to the next.
Les pics d'amplitude alignés en oblique en figure 4 sont de cette façon alignés sur des lignes perpendiculaires aux lignes de balayage, comme représenté en figure 5, ce à quoi correspondrait la disposition relative de bâtonnets représentée en figure 6, avec des lignes de balayage qui seraient rigoureusement perpendiculaires aux bâtonnets.The amplitude peaks aligned obliquely in Figure 4 are in this way aligned on lines perpendicular to the scan lines, as shown in Figure 5, which would correspond to the relative arrangement of sticks represented in FIG. 6, with scanning lines which would be strictly perpendicular to the sticks.
On peut établir une corrélation entre l'agencement des signaux en figure 5 et la disposition des bâtonnets en figure 6, en faisant un cumul ou une somme des amplitudeβ des pics transversalement alignés détectés sur des lignes de balayage successives. Lorsque le point d'impact du faisceau lumineux sur l'enveloppe 10 a une dimension qui correspond sensiblement au pas entre les lignes de balayage, le cumul des amplitudes des pics relatifs à un même bâtonnet correspondra sensiblement à l'amplitude d'un signal produit par un photodétecteur recevant l'image d'un bâtonnet conformément à la technique décrite dans le brevet français antérieur précité, toutes autres choses étant égales par ailleurs. En d'autres termes, la détection des bâtonnets représentés en figure 6 par le dispositif antérieur, et la détection des bâtonnets représentés en figure 3 par le dispositif selon l'invention, produiront des signaux de même type, qui pourront être traités de façon semblable.A correlation can be established between the arrangement of the signals in FIG. 5 and the arrangement of the rods in FIG. 6, by making a sum or a sum of the amplitudes β of the transversely aligned peaks detected on successive scanning lines. When the point of impact of the light beam on the envelope 10 has a dimension which corresponds substantially to the pitch between the scanning lines, the sum of the amplitudes of the peaks relating to the same rod will correspond substantially to the amplitude of a signal produced by a photodetector receiving the image of a stick in accordance with the technique described in the aforementioned prior French patent, all other things being equal. In other words, the detection of the rods represented in FIG. 6 by the prior device, and the detection of the rods represented in FIG. 3 by the device according to the invention, will produce signals of the same type, which can be processed in a similar manner .
Pour renforcer encore cette similitude, on peut prévoir que le cumul des amplitudes des pics alignés correspondant à un même bâtonnet, soit pondéré au moyen du nombre de lignes de balayage sur lesquelles on a détecté un pic d'amplitude pour ce bâtonnet, ce qui permettra de tenir compte de la ressemblance de la forme graphique à un bâtonnet, tout en associant à ce bâtonnet uniquement deux informations (sa position et l'amplitude du signal détecté).To further reinforce this similarity, provision can be made for the cumulative amplitudes of the aligned peaks corresponding to the same rod to be weighted by means of the number of scanning lines on which an amplitude peak has been detected for this rod, which will allow to take into account the resemblance of the graphic form to a stick, while associating with this stick only two pieces of information (its position and the amplitude of the detected signal).
On se réf rera maintenant à la figure 7, qui représente schématiquement un dispositif de lecture selon l'invention.We will now refer to FIG. 7, which schematically represents a reading device according to the invention.
Ce dispositif comprend une source lumineuse 28, telle qu'un laser à argon, une lampe à quartz ou à iode et un filtre associé ou encore un ensemble laser semi-conducteur et doubleur de fréquence. Le faisceau lumineux 30 cylindrique produit par cette source est renvoyé, par un miroir 32, sur un miroir polygonal 34 monté à rotation autour d'un axe 36 parallèle à la surface de la lettre 10 balayer.This device comprises a light source 28, such as an argon laser, a quartz or iodine lamp and an associated filter or also a semiconductor laser and frequency doubler assembly. The cylindrical light beam 30 produced by this source is returned, by a mirror 32, to a polygonal mirror 34 rotatably mounted about an axis 36 parallel to the surface of the letter 10 to sweep.
Le miroir polygonal 34 est en fait un miroir annulaire à facettes planes 38 ayant un angle au centre de 10° par exemple, ce qui correspond à un nombre de facettes égales à 36 pour le miroir 34, et à une déviation du faisceau de 20°.The polygonal mirror 34 is in fact an annular mirror with plane facets 38 having an angle at the center of 10 ° for example, which corresponds to a number of facets equal to 36 for the mirror 34, and to a deflection of the beam of 20 ° .
Le faisceau lumineux 30 est réfléchi par chaque facette 38 sur un miroir 40 de très faible surface qui le renvoie sur l'enveloppe 10 à balayer. Le miroir 34 est entraîné en rotation autour de l'axe 36 dans le sens indiqué par la flèche, de telle sorte que le faisceau lumineux est initialement réfléchi comme indiqué entre 30, , puis finalement en 30„, en parcourant une ligne de balayage L entre ces deux positions. : Le faisceau lumineux réfléchi par la surface de l'enveloppe 10 est récupéré par un objectif 42 à grand champ et grande profondeur de champ, permet¬ tant de former une image de la ligne de balayage L sur la fenêtre d'entrée 44 d'un anamorphoseur 46, en particulier du type à fibres optiques, qui transforme l'image de la ligne de balayage L en une surface .circulaire adaptée à la fenêtre d'entrée d'un photodétecteur 48. Eventuellement, un objectif? 50- est interposé entre la sortie de l'anamorphoseur 46 et le ptrotorfëteπteur 48r pour réaliser une adaptation de dimension d'image. Un filtre 52 de- sélection du spectre de fluorescence est par ailleurs placé devant le photodétecteur 48. L'ensemble optique comprenant le miroir de renvoi 32, le miroir polygonal rotatif 34, le miroir de renvoi 40, l'objectif 42, l'anamorphoseur 46, l'optique 50, le filtre 52 et le photodétecteur 48, est porté par une platine montée à rotation autour d'un axe transversal de pivotement 54 qui est parallèle à la surface de l'enveloppe 10 et perpendiculaire à l'axe 36 précité. Si l'on veut éviter d'entraîner en rotation la source lumineuse 28, l'axe 54 peut être sensiblement aligné avec l'axe du faisceau lumineux 30 en sortie de la source 28.The light beam 30 is reflected by each facet 38 on a mirror 40 of very small area which returns it to the envelope 10 to be scanned. The mirror 34 is driven in rotation about the axis 36 in the direction indicated by the arrow, so that the light beam is initially reflected as indicated between 30, and finally in 30 „, traversing a scanning line L between these two positions. : The light beam reflected by the surface of the envelope 10 is recovered by a lens 42 with a large field and a large depth of field, so much as to form an image of the scanning line L on the input window 44 of an anamorphoser 46, in particular of the fiber optic type, which transforms the image of the scanning line L into a circular surface adapted to the input window of a photodetector 48. Possibly, an objective? 50- is interposed between the output of the anamorphoser 46 and the ptrotorfëteπteur 48 r to achieve an adaptation of image size. A filter 52 for selecting the fluorescence spectrum is also placed in front of the photodetector 48. The optical assembly comprising the deflection mirror 32, the rotary polygon mirror 34, the deflection mirror 40, the objective 42, the anamorphoser 46, the optics 50, the filter 52 and the photodetector 48, is carried by a plate mounted for rotation about a transverse pivot axis 54 which is parallel to the surface of the envelope 10 and perpendicular to the axis 36 cited above. If one wishes to avoid driving the light source 28 in rotation, the axis 54 can be substantially aligned with the axis of the light beam 30 at the output of the source 28.
En variante, il est possible de ne pas déplacer l'ensemble optique, mais d'interposer un miroir pivotant 100 de surface adéquate sur le trajet 30, , 302 de balayage et de récupération de la lumière émise par fluorescence. Il faut par ailleurs mentionner que les miroirs 32 et 40 n'ont d'autre raison fonctionnelle que de rendre compact le montage optique mais n'intervien¬ nent pas dans le procédé selon l'invention. Ce dispositif selon l'invention comprend également, pour déterminer sur 0 chaque ligne de balayage un point de référence dont la position fixe est connue, une fibre optique 56 dont une extrémité se trouve placée sur le trajet du faisceau lumineux 30, au début de la ligne de balayage et dont l'autre extrémité est associée, par exemple par un objectif 58, à la fenêtre d'entrée d'un photodétecteur 60. Le passage du faisceau lumineux 30, sur 5 l'extrémité de la fibre 56 produira, par l'intermédiaire du photodétecteur 60, un top de synchronisation qui pourra être considéré comme un point de référence de position connue sur chaque ligne de balayage. Bien entendu, la fibre optique 56, et éventuellement l'objectif 56 ou le photodétecteur 60, devront suivre le mouvement de rotation autour de l'axeAs a variant, it is possible not to displace the optical assembly, but to interpose a pivoting mirror 100 of suitable surface on the path 30,, 30 2 for scanning and recovering the light emitted by fluorescence. It should also be mentioned that the mirrors 32 and 40 have no other functional reason than to compact the optical assembly but do not intervene in the method according to the invention. This device according to the invention also comprises, to determine on 0 each scanning line a reference point whose fixed position is known, an optical fiber 56, one end of which is placed in the path of the light beam 30, at the start of the scanning line and the other end of which is associated, for example by a lens 58, with the input window of a photodetector 60. The passage of the light beam 30, over 5 the end of the fiber 56 will produce, by via the photodetector 60, a synchronization signal which can be considered as a reference point of known position on each scanning line. Of course, the optical fiber 56, and possibly the objective 56 or the photodetector 60, will have to follow the rotational movement around the axis
54.54.
Pour tenir compte des variations de hauteur des piles de lettres, on prévoitTo take into account variations in the height of the stacks of letters,
5 qu'il faut utiliser un objectif 42 permettant de lire, au niveau de la lettre 10, un point d'impact du faisceau lumineux ayant un diamètre de quelques dixièmes de millimètres sur une profondeur de champ d'au moins 120 mm.5 that it is necessary to use a lens 42 making it possible to read, at the level of the letter 10, a point of impact of the light beam having a diameter of a few tenths of a millimeter over a depth of field of at least 120 mm.
Par ailleurs, la surface de balayage parcourue par le point d'impact duFurthermore, the scanning surface traversed by the point of impact of the
2 faisceau lumineux est de 200 x 250 mm . Si le pas entre lignes de balayage2 light beam is 200 x 250 mm. If the pitch between scan lines
10 est de 0,5 mm, on arrive à 400 lignes de balayage d'une longueur de 250 mm chacune. La durée de balayage correspondante est comprise entre quelques dixièmes de secondes et une seconde environ.10 is 0.5 mm, 400 scanning lines with a length of 250 mm each are arrived at. The corresponding scanning time is between a few tenths of a second and about one second.
On fera maintenant référence à la figure 8, qui représente schématiquement les circuits de traitement des signaux produits par les photodétecteurs 48 etReference will now be made to FIG. 8, which schematically represents the circuits for processing the signals produced by the photodetectors 48 and
15 60.15 60.
La sortie du photodétecteur 48 est reliée par un amplificateur 62 à un filtre passe-bas 64 dont la sortie est reliée d'une part à un convertisseur analogique-numérique 66 et d'autre part à un dérivateur 68 associé à un circuit 70 de détection des fronts de signaux dont la sortie est reliée, d'une 0 part, au convertisseur analogique-numérique 66 et, d'autre part, à l'entrée d'une mémoire FIFO (Firt In-First Out) (multi-registre à décalage) 72 à une autre entrée de laquelle est également reliée la sortie du convertisseur analogique-numérique 66. Le photodétecteur 60 de repérage d'un point fixe de début de ligne de balayage est relié par un circuit déclencheur 74 d'une part à un compteur 76 de numéro de ligne et d'autre part à l'entrée de remise à zéro d'un compteur 78 piloté par une horloge 80. Les sorties des compteurs 76 à 78 sont reliées à des entrées de la mémoire FIFO 72. Celle-ci est associée à un micro-processeur 82 raccordé à une interface de ϋ communication 84 et commandant des circuits d'asservissement 86 et 88 des moteurs électriques 90 et 92 d'entraînement du miroir polygonal tournant 34 et de l'ensemble optique monté en rotation autour de l'axe 54. Ces circuits fonctionnent de la façon générale suivante : Les variations d'amplitude du signal produit par le photodétecteur 48 sont traitées par l'amplificateur 62 et le filtre passe-bas 64 puis sont numérisées par le convertisseur 66 avant d'être enregistrées dans la mémoire 72. Le dérivateur 68 associé au circuit 70 de détection des fronts permet de différencier les signaux numérisés correspondant à des pics d'amplitude du signal du photodétecteur et ceux correspondant à des creux entre lesquels sont situés des pics d'amplitude et de déclencher le convertisseur 66. Par ailleurs, le photodétecteur 60 permet de compter les lignes de balayage ~ par l'intermédiaire du déclencheur 74 et du compteur 76 et de remettre à zéro le compteur 78 au début de chaque ligne de balayage. L'horloge 80 permet de repérer sur chaque ligne de balayage la position des pics et creux d'amplitude enregistrés dans la mémoire 72. Le micro-processeur 82 pilote les moteurs 90 et 92 par l'intermédiaire des 0 circuits, d'asservissement 86 et 88, puis acquiert dans la mémoire 72 les amplitudes? dès. piles et des creux des signaux du photodétecteur 48, ainsi que leur- position, (numéros des lignes de balayage et position des pics et des creux dans les lignes de balayage). Un logiciel, enregistré dans une mémoire associée au micro-processeur 82, 5 permet de réaliser les traitements suivants :The output of the photodetector 48 is connected by an amplifier 62 to a low-pass filter 64, the output of which is connected on the one hand to an analog-digital converter 66 and on the other hand to a differentiator 68 associated with a detection circuit 70 signal edges whose output is connected, on the one hand, to the analog-digital converter 66 and, on the other hand, to the input of a FIFO (Firt In-First Out) memory (multi-register with offset) 72 to another input to which the output of the analog-digital converter 66 is also connected. The photodetector 60 for locating a fixed point at the start of the scanning line is connected by a trigger circuit 74 on the one hand to a line number counter 76 and on the other hand to the reset input of a counter 78 controlled by a clock 80. The outputs of the counters 76 to 78 are connected to inputs of the FIFO memory 72. This this is associated with a microprocessor 82 connected to an interf ace of ϋ communication 84 and controlling the servo circuits 86 and 88 of the electric motors 90 and 92 for driving the rotating polygonal mirror 34 and the optical assembly mounted in rotation about the axis 54. These circuits operate from the generally as follows: The variations in amplitude of the signal produced by the photodetector 48 are processed by the amplifier 62 and the low-pass filter 64 then are digitized by the converter 66 before being recorded in the memory 72. The differentiator 68 associated with circuit 70 for detecting fronts makes it possible to differentiate the digitized signals corresponding to amplitude peaks of the photodetector signal and those corresponding to valleys between which amplitude peaks are located and trigger the converter 66. Furthermore, the photodetector 60 makes it possible to count the scanning lines ~ via trigger 74 and counter 76 and reset counter 78 at the start of each scan line. The clock 80 makes it possible to locate on each scanning line the position of the peaks and troughs of amplitude recorded in the memory 72. The microprocessor 82 controls the motors 90 and 92 via the 0 circuits, of servo-control 86 and 88, then acquires in memory 72 the amplitudes? soon. batteries and dips of the signals from the photodetector 48, as well as their position, (numbers of the scanning lines and position of the peaks and dips in the scanning lines). Software, stored in a memory associated with the microprocessor 82, 5 makes it possible to carry out the following treatments:
- calculer les amplitudes des pics significatifs des signaux du photodétecteur 48 (amplitude du pic - demi-somme des amplitudes des creux adjacents).calculating the amplitudes of the significant peaks of the signals from the photodetector 48 (amplitude of the peak - half-sum of the amplitudes of the adjacent troughs).
- corriger la position des pics significatifs dans le cas où les lignes de balayage sont orientées obliquement par rapport à la direction des bâtonnets u du code- correct the position of significant peaks in the case where the scanning lines are oriented obliquely with respect to the direction of the rods u of the code
- mémoriser ces informations- memorize this information
- faire la somme ou le cumul des informations obtenues sur chaque ligne de balayage (somme des amplitudes des pics de position concordante sur des lignes de balayage successives), et associer à cette information la position 5 du pic d'amplitude correspondant et le nombre de lignes de balayage concernées- sum or accumulate the information obtained on each scan line (sum of the amplitudes of the peaks of concordant position on successive scan lines), and associate with this information the position 5 of the corresponding amplitude peak and the number of relevant scan lines
- identifier la structure du code d'indexation, soit à partir de groupes de trois: informations (position, somme des amplitudes des pics et nombre de lignes de balayage) soit à partir de groupes de deux informations (position u des pics d'amplitude et amplitude de ces pics, pondérée au moyen du nombre de lignes de balayage concernées).- identify the structure of the indexing code, either from groups of three: information (position, sum of the amplitudes of the peaks and number of scan lines) or from groups of two information (position u of the amplitude peaks and amplitude of these peaks, weighted by the number of scan lines concerned).
L'un des avantages de l'invention est que le logiciel propre à effectuer ce traitement est très peu différent du logiciel associé au procédé et au dispositif décrits dans le brevet français antérieur précité, de sorte que - l'homme du métier, pour la mise en oeuvre de l'invention, se contentera d'une adaptation du logiciel connu. L'invention est applicable aussi bien à la lecture et à la reconnaissance des codes d'indexation figurant sur des plis postaux, que des codes barres figurant sur des étiquettes d'objets ou produits divers, sur des chèques, et autres documents. One of the advantages of the invention is that the software suitable for carrying out this processing is very little different from the software associated with the method and the device described in the aforementioned prior French patent, so that - the person skilled in the art, for the implementation of the invention, will be satisfied with an adaptation of the known software. The invention is applicable both to the reading and to the recognition of indexing codes appearing on postal envelopes, as bar codes appearing on labels of various objects or products, on checks, and other documents.

Claims

mm
REVENDICAπONS
1) Procédé de lecture d'un code barres sur un support sensiblement immobi¬ le, consistant à balayer au moins une partie de la surface du support (10) au moyen d'un faisceau lumineux, à recevoir sur un photodétecteur (48) le faisceau renvoyé par la surface du support (10) et à enregistrer les variations d'amplitude du signal produit par le photodétecteur ainsi que leur position, pour en déduire la structure du code barres (16), caractérisé en ce qμîill consiste à balayer la surface du support (10) selon une trame de lignes (LU,. HZ,. L3,...) par déplacement de l'impact sensiblement ponctuel d'un faisceau lumineux (30, , 30..), suivant des lignes sensiblement parallèles à TJ. une même direction fixe prédéterminée, et se succédant à un intervalle prédéterminé, à détecter pour chaque ligne de balayage les pics d'amplitude du signal du photodétecteur (48) et à faire un cumul des amplitudes des pics de position concordante dans des lignes successives pour identifier la position et éventuellement le type de chaque barre code et pour la 5 diff rencier d'éventuels signaux parasites.1) Method for reading a bar code on a substantially immobible support, consisting in scanning at least part of the surface of the support (10) by means of a light beam, to be received on a photodetector (48) on beam returned by the surface of the support (10) and recording the variations in amplitude of the signal produced by the photodetector as well as their position, to deduce the structure of the bar code (16), characterized in that qμîill consists in scanning the surface of the support (10) along a grid of lines (LU ,. HZ ,. L3, ...) by displacement of the substantially punctual impact of a light beam (30,, 30 ..), along substantially parallel lines at TJ. the same predetermined fixed direction, and succeeding each other at a predetermined interval, detecting for each scanning line the amplitudes of the signal from the photodetector (48) and accumulating the amplitudes of the peaks of concordant position in successive lines for identify the position and possibly the type of each bar code and for the 5 differentiation of any spurious signals.
2) Procédé selon la revendication 1, caractérisé en ce que la vitesse de balayage est constante, et les positions des pics d'amplitude sont repérées par un comptage de temps.2) Method according to claim 1, characterized in that the scanning speed is constant, and the positions of the amplitude peaks are identified by a time count.
3) Procédé selon la revendication 1 ou 2, caractérisé en ce que les lignes de 0 balayage (Ll, L2, L3,...) coupant en oblique les barres (18) du code, il consiste à compenser les décalages des pics d'amplitude (24) d'une ligne à la suivante, pour reconstituer des pics d'amplitude alignés entre eux sur des lignes perpendiculaires aux lignes de balayage.3) Method according to claim 1 or 2, characterized in that the scanning lines (L1, L2, L3, ...) obliquely cutting the bars (18) of the code, it consists in compensating for the offsets of the peaks d amplitude (24) from one line to the next, to reconstruct amplitude peaks aligned with each other on lines perpendicular to the scanning lines.
4) Procédé selon la revendication 3, caractérisé en ce qu'il consiste à 5 repérer sur chaque ligne de balayage un point de position fixe connue, et à déplacer par rapport à ce point les pics d'amplitude (24) d'une ligne, d'une distance fonction de l'angle des lignes de balayage par rapport aux barres (18) du code, pour aligner ces pics perpendiculairement à la ligne avec les pics d'amplitude de position concordante des lignes voisines ou adjacentes. 0 5) Procédé selon l'une des revendications 1 à 4, caractérisé en ce que les lignes de balayage coupent, selon l'orientation du support (10), les barres du code=,. avec un angle compris entre des valeurs limites prédéterminées qui sont par exemple d'environ + et - 30 ou 40° par rapport à la direction perpendiculaire aux barres du code.4) Method according to claim 3, characterized in that it consists in locating on each scanning line a point of known fixed position, and in moving with respect to this point the amplitude peaks (24) of a line , from a distance as a function of the angle of the scanning lines relative to the bars (18) of the code, in order to align these peaks perpendicular to the line with the peaks of amplitude of concordant position of the neighboring or adjacent lines. 0 5) Method according to one of claims 1 to 4, characterized in that the scanning lines intersect, according to the orientation of the support (10), the bars of the code = ,. with an angle between predetermined limit values which are for example approximately + and - 30 or 40 ° relative to the direction perpendicular to the code bars.
6) Procédé selon l'une des revendications précédentes, caractérisé en ce qu'il consiste à balayer toute la surface du support portant le code barres.6) Method according to one of the preceding claims, characterized in that it consists in scanning the entire surface of the support carrying the barcode.
7) Procédé selon l'une des revendications précédentes, caractérisé en ce que, la dimension, dans une direction perpendiculaire aux lignes de balayage, de l'impact du faisceau lumineux sur la surface du support (10) est du même ordre de grandeur que le pas des lignes de balayage.7) Method according to one of the preceding claims, characterized in that the dimension, in a direction perpendicular to the scanning lines, of the impact of the light beam on the surface of the support (10) is of the same order of magnitude as the pitch of the scan lines.
8) Procédé selon l'une des revendications 1 à 7, caractérisé en ce qu'il consiste à pondérer chaque cumul des amplitudes des pics de position - concordantes au moyen d'un facteur dépendant du nombre de lignes de fralayage sur lesquelles ont été détectés les pics d'amplitude concernés.8) Method according to one of claims 1 to 7, characterized in that it consists in weighting each cumulation of the amplitudes of the position peaks - concordant by means of a factor depending on the number of scour lines on which have been detected the amplitude peaks concerned.
9) Procédé selon l'une des revendications précédentes, caractérisé en ce que, pour déterminer l'amplitude d'un pic précité, il consiste à soustraire de la valeur maximale d'amplitude mesurée du pic, la demi-somme des valeurs minima d'amplitude entre lesquelles est situé le pic.9) Method according to one of the preceding claims, characterized in that, to determine the amplitude of an aforementioned peak, it consists in subtracting from the maximum measured amplitude value of the peak, the half-sum of the minimum values d amplitude between which the peak is located.
10) Procédé selon l'une des revendications 1 à 9, caractérisé en ce que, pour réaliser le balayage en lignes successives parallèles de la surface du support, il consiste à monter pivotant, autour d'un axe sensiblement parallèle à la surface du support (10), un ensemble optique comprenant au moins un miroir (40 ou 100) de renvoi du faisceau lumineux (30) vers la surface du support (10).10) Method according to one of claims 1 to 9, characterized in that, to carry out the scanning in successive parallel lines of the surface of the support, it consists of pivotally mounting, about an axis substantially parallel to the surface of the support (10), an optical assembly comprising at least one mirror (40 or 100) for returning the light beam (30) to the surface of the support (10).
11) Procédé selon la revendication 10, caractérisé en ce que l'ensemble optique monté pivotant comprend également le photodétecteur (48) et des moyens optiques (42,46,50,52) de réception du faisceau lumineux renvoyé par la surface du support (10).11) Method according to claim 10, characterized in that the pivotally mounted optical assembly also comprises the photodetector (48) and optical means (42,46,50,52) for receiving the light beam returned by the surface of the support ( 10).
12) Procédé selon l'une des revendications 1 à 11, caractérisé en ce qu'il consiste à déplacer le point d'impact du faisceau lumineux (30) sur une ligne L de la surface du support (10) au moyen d'un miroir polygonal tournant (34) interposé entre une source lumineuse (28) et un miroir (40) de renvoi vers la surface du support (10).12) Method according to one of claims 1 to 11, characterized in that it consists in moving the point of impact of the light beam (30) on a line L of the surface of the support (10) by means of a rotating polygonal mirror (34) interposed between a light source (28) and a mirror (40) returning towards the surface of the support (10).
13) Dispositif de lecture d'un code barres sur un support sensiblement immobile, destiné en particulier à l'exécution du procédé selon l'une des revendications précédentes, comprenant une source lumineuse (28), des moyens optiques (32,34,40) de projection d'un faisceau lumineux (30) issu de la source sur la surface du support (10), des moyens optiques (40,46,50,52) de transmission du faisceau renvoyé par la surface du support (10), des moyens photodétecteurs (48) de réception du faisceau renvoyé, et des moyens de traitement des signaux reproduits par les moyens photodétecteurs, caracté¬ risé en ce qu'il comprend des moyens optiques (34) pour déplacer le point d'impact du faisceau lumineux (30) sur la surface du support (10) selon une trame de lignes sensiblement parallèles à une direction fixe prédéterminée, se succédant à un intervalle prédéterminé et en ce que les moyens de traitement de signaux comprennent des moyens (72) d'enregistrement des pics d'amplitude des signaux correspondant aux différentes lignes de balaya¬ ge, et des moyens de cumul des amplitudes des pics de position concordante détectés sur des lignes successives. 14) Dispositif selon la revendication 13, caractérisé en ce que les moyens de traitement des signaux comprennent des moyens de calcul pour compenser les décalages d'une ligne à l'autre des pics d'amplitude correspondant à une même barre coupée en oblique par les lignes de balayage.13) Device for reading a bar code on a substantially stationary support, intended in particular for carrying out the method according to one of the preceding claims, comprising a light source (28), optical means (32,34,40 ) projecting a light beam (30) from the source onto the surface of the support (10), optical means (40,46,50,52) for transmitting the beam returned by the surface of the support (10), photodetector means (48) for receiving the returned beam, and means for processing of the signals reproduced by the photodetector means, characterized in that it comprises optical means (34) for moving the point of impact of the light beam (30) on the surface of the support (10) according to a grid of lines substantially parallel to a predetermined fixed direction, succeeding each other at a predetermined interval and in that the signal processing means comprise means (72) for recording peaks of amplitude of the signals corresponding to the different scanning lines, and means for accumulating the amplitudes of the peaks of concordant position detected on successive lines. 14) Device according to claim 13, characterized in that the signal processing means comprise calculation means to compensate for the offsets from one line to another of the amplitude peaks corresponding to the same bar cut obliquely by the scan lines.
15) Dispositif selon la revendication 13 ou 14, caractérisé en ce qu'il comprend des moyens (56,60) de repérage d'un point fixe de position connue sur chaque ligne de balayage, tels par exemple qu'une fibre optique (56) dont une extrémité est placée sur la ligne de balayage et dont l'autre extrémité est associée à un photodétecteur (60).15) Device according to claim 13 or 14, characterized in that it comprises means (56,60) for locating a fixed point of known position on each scanning line, such as for example an optical fiber (56 ) one end of which is placed on the scanning line and the other end of which is associated with a photodetector (60).
16) Dispositif selon l'une des revendications 13 à 15, caractérisé en ce qu'il comprend un ensemble optique monté pivotant autour d'un axe (54) parallèle à la surface du support et comprenant au moins un miroir (40) de renvoi du faisceau lumineux à la surface du support.16) Device according to one of claims 13 to 15, characterized in that it comprises an optical assembly mounted pivoting about an axis (54) parallel to the surface of the support and comprising at least one mirror (40) of return of the light beam on the surface of the support.
17) Dispositif selon la revendication 16, caractérisé en ce que l'ensemble optique pivotant comprend également les moyens (42,46,50,52) de transmis- sion du faisceau renvoyé par la surface du support, et les moyens photodé¬ tecteurs (48) précités.17) Device according to claim 16, characterized in that the pivoting optical assembly also comprises the means (42,46,50,52) for transmitting the beam returned by the surface of the support, and the photodé¬ vector means ( 48) cited above.
18) Dispositif selon la revendication 16 ou 17, caractérisé en ce qu'il comprend un moteur électrique d'entraînement de l'ensemble optique en rotation autour dudit axe (54). 19) Dispositif selon l'une des revendications 16 à 18, caractérisé en ce que le miroir (40) de renvoi du faisceau lumineux est associé à un miroir polygonal tournant (34), interposé entre le miroir de renvoi (40) et une source lumineuse (28).18) Device according to claim 16 or 17, characterized in that it comprises an electric motor for driving the optical assembly in rotation about said axis (54). 19) Device according to one of claims 16 to 18, characterized in that the mirror (40) for returning the light beam is associated with a rotating polygonal mirror (34), interposed between the return mirror (40) and a source luminous (28).
20) Dispositif selon la revendication 19, caractérisé en ce qu'il comprend un moteur électrique d'entraînement du miroir polygonal tournant (34).20) Device according to claim 19, characterized in that it comprises an electric motor for driving the rotating polygonal mirror (34).
21) Dispositif selon l'ensemble des revendications 19 et 20, caractérisé en ce que ces moteurs électriques sont commandés par un micro-processeur (82) faisant partie des moyens précités de traitement de signaux. 21) Device according to all of claims 19 and 20, characterized in that these electric motors are controlled by a microprocessor (82) forming part of the aforementioned signal processing means.
EP89905708A 1988-05-10 1989-05-10 Method and device for reading a bar code on a substantially motionless medium Withdrawn EP0377006A1 (en)

Applications Claiming Priority (2)

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FR8806315A FR2631476B1 (en) 1988-05-10 1988-05-10 METHOD AND DEVICE FOR READING A BAR CODE ON A SUBSTANTIALLY IMMOBILE MEDIUM
FR8806315 1988-05-10

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EP (1) EP0377006A1 (en)
JP (1) JPH02504193A (en)
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WO (1) WO1989011131A1 (en)

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FR2631476A1 (en) 1989-11-17
FR2631476B1 (en) 1992-01-03
WO1989011131A1 (en) 1989-11-16
JPH02504193A (en) 1990-11-29
US5155344A (en) 1992-10-13

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