FR2930636A1 - Mail processing machine, has optical reading assembly acquiring image of mail item during displacement of mail item through machine, and processing unit or local processing unit determining width and length of mail item from image - Google Patents

Abstract

The machine has transportation units constituted by a feeding/extracting module and a weighted module for transporting a mail item (24) i.e. mail, respectively having length and width, to a stamping module. An optical reading assembly acquires an image of the mail item during displacement of the mail item through the machine and is connected to a local processing unit. A processing unit or the local processing unit determines the width and the length of the mail item from the image. An independent claim is also included for a method for measuring dimensions of a mail item on fly in a mail processing machine.

Description

The present invention relates exclusively to the field of mail processing and more particularly relates to a method for measuring the dimensions of mail items when they are moved in a mail processing machine.

PRIOR ART The pricing of mail items is based on criteria of weight and / or dimensions of the mail items (thickness, length and / or width of the envelope). The dimensions of mail items are therefore important parameters in franking machines and other mail processing machines. Indeed, many postal services depend on the format of mail items and it is then a question of verifying that this format is greater than thresholds or of checking that the ratio between the length and the width of the article of mail is between two limits (examples: 1.3 <R <2.5 for the USA, R <- / 2 for Germany). For measuring the length and the width of an envelope, it is known to determine three ranges of values by means of two presence detectors each indicating whether or not the envelope has passed on the detector. However, the position of these detectors varies according to the postal regulations to be applied and therefore requires adaptation to local regulations which is relatively expensive. That is why was developed in EPO application 871 145 a device implementing a plurality of juxtaposed presence detectors spaced each of the two adjacent detectors from a given distance and which responds, regarding the width of the mail items, to this multiplicity of local regulations. However, the accuracy of this device remains limited to the distance between two adjacent detectors, about one millimeter and its cost is unfortunately prohibitive for entry-level machines. In addition, it does not allow, without the addition of additional means (front detector of the mail item and incremental encoder), also a measurement of the length of the mail items.35 Object and definition of the invention The present invention therefore aims to overcome the aforementioned drawbacks with a method of measuring the dimensions of a mail piece allowing a universal and low-cost measurement of the width of a mail article during its movement in a processing machine. mail. An object of the invention is also to provide a measurement method which also allows a measurement of the length of these mail items. Another object of the invention is also to propose a measurement method whose means of implementation do not require a redefinition of the general architecture of the franking machine. These goals are achieved by a method of measuring the theft of the dimensions of a mail item in a mail processing machine comprising the following steps: obtaining an image of each of these mail items as they move through the machine, and. from these successive images, determining the width of each of these mail items. In a preferred embodiment, said step of acquiring an image of the mail item includes acquiring a vertical line of pixels of that image and said processing step determines said width of the article of mail. mail by comparing the value of each of said pixels to a predetermined threshold. The method of the invention further advantageously comprises a step of determining the length of each of said mail items from these successive images. Preferably, said step of acquiring an image of the mail article comprises acquiring a predetermined number of vertical lines of pixels of this image and said processing step determines said length of the mail article by comparing the value of each of said pixels forming said vertical lines with a predetermined threshold value. Thus, by acquiring in its entirety or line after line the image of the mail item as it moves through the mail processing machine, it is possible to determine with very great precision both the width and the length. of each mail item.

Advantageously, said step of acquiring an image of the mail item is performed by a contact image sensor formed of an integrated module comprising a line of adjacent semiconductor detection cells, a collimation optics and a lighting system that allows A4 scanning. To enable scanning of a larger size mail article, said contact image sensor may be moved away from a reference wall by a predetermined distance corresponding at most to the smallest mailpiece width. to be treated or arranged in series with at least one other contact image sensor. The present invention also relates to a mail processing machine comprising: means for conveying mail items each having a specified length and width to postage means,. means for acquiring an image of each of these mail items as they move through the machine, and. processing means for determining, from these successive images, the width of each of these mail items. Said means for acquiring an image advantageously comprise means for acquiring a vertical line of pixels of this image and said processing means determine said width of the mail article by comparing the value of each of said pixels with a predetermined threshold. Said processing means can also determine the length of each of said mail items from these successive images. Said means for acquiring an image advantageously comprise means for acquiring a predetermined number of vertical lines of pixels of this image and said processing means determine said length of the mail article by comparing the value of each of said pixels forming said vertical lines with a predetermined threshold value. Preferably, said image acquisition means comprise a linear image sensor arranged perpendicular to the direction of movement of said mailpieces.

According to the embodiment envisaged, said linear image sensor can be vertically movable and move in synchronism with at least one mobile transport roller of a supply module of said mail processing machine or else be fixed and mounted under the transport path of a weighing module of said mail processing machine.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood in view of the following detailed description accompanied by illustrative and nonlimiting examples with reference to the following figures in which: FIG. 1 is a schematic view of a first embodiment of a device for measuring the dimensions of a mailpiece according to the invention, 15. FIG. 2 is a schematic view of a second embodiment of a device for measuring the dimensions of a mail item according to the invention, FIG. 3 shows the light intensity level curves obtained by the optical reading means of the device of FIGS. 1 and 2 during the displacement of a mail item, and Figure 4 schematically illustrates the internal structure of a mail processing machine of the prior art.

DETAILED DESCRIPTION OF EMBODIMENTS As illustrated in FIG. 4, a prior art mail processing machine 10 conventionally comprises from upstream to downstream (depending on the direction of travel of the mail items through the machine). a supply / extraction module 12 provided with a receiving tray 120 intended to receive a stack of mail items, preferably of different formats (so-called mixed mail mode), and comprising a first series of transport rollers 122A 122B for driving these mailpieces downstream and against a reference wall (also called foldguide and illustrated in FIG. 3) first in a separation zone comprising superimposed extraction rollers 124A, 124B 35 preceded by a die 126 and wherein these mail items are automatically extracted one by one from the stack and then in a transport area comprising a second set of transport rolls fo for example two adjacent sets of superimposed front transport rollers 128A, 128B and rear 130A, 130B for conveying the mail items thus extracted one by one downstream of the supply / extraction module 12, for example to a weighing module 14 or when it is absent directly to a franking module 16 of these mail items. As is known, the upper rollers 128B, 130B of these transport rollers are mounted idle and vertically movable to accommodate the different thicknesses of the mail items and the set of lower rollers is motorized. The dynamic weighing module 14 interposed between the feed / extraction module 12 and the franking module 16 comprises a weighing plate 140 incorporating a load cell and supporting one or more belts or drive belts 142 for transporting the goods. mail items from a position upstream of this plateau to a downstream position. The mail items are held on the weighing pan 140 by resilient support members 144A, 144B, 144C disposed one behind the other in the direction of travel of the mail items and intended, during the transportation of mail items of this position upstream to this position downstream, to press these mail items against the drive bands of the weighing plate and against a longitudinal vertical wall not shown forming a reference wall arranged in continuity with that of the module of supply / extraction.

The franking module 16 comprises, in a known manner, an ink jet printing module 160 for printing a postal imprint on each previously selected (and possibly weighed) mail article and, for conveying each article mail to be franked and then cleared, both upstream conveying means advantageously comprising upstream conveyor rollers and counter-rollers 162A, 162B and downstream conveying means preferably comprising downstream conveyor rollers and counter-rollers 164A, 164B. Of course, this mail processing machine further comprises firstly a general processing unit 18 (generally memory and microprocessor) for managing the printing and conveying of mail items through the machine, the along its transport path, and secondly a detector 166 of the position of these mail items (advantageously from the front of the mail item) connected to this general processing unit and from which the printing of the The postal fingerprint is synchronized (based on a predefined standard offset defining a predetermined location for printing). According to a first embodiment of the invention illustrated diagrammatically in FIG. 1, the supply / extraction module 12 furthermore comprises, for measuring the length and the width of the mailpieces, an optical reading assembly. 20 allowing in connection with a local processing unit 22 an automatic acquisition of the image of each of the mail items scrolling in front of this optical reading assembly. This assembly is movable in synchronism with at least one 128B of the mobile transport rollers to reduce shocks related to the passage of mail items and thus ensure processing of mail items, regardless of their thickness, especially in the presence of thick envelopes. The material structure of the mobile optical reading assembly 20 has been the subject of the application FR 07 57285 previously filed in the name of the applicant and therefore will not be described in more detail. It will be recalled only that this mobile assembly comprises, mounted between an upstream deflector and a downstream deflector, a contact image sensor 20A (CIS: contact image sensor) of linear type whose length is designed to allow image acquisition. in A4 format, ie a maximum mail article width of approximately 216 mm. This linear optical sensor is typically an integrated module comprising a line of adjacent CCD or CMOS semiconductor detection cells (whose spacing is a function of the desired resolution, for example 0.127 mm (7.9 pixels / mm) for a resolution of 200 dpi), a collimation optics and a lighting system that when activated illuminates the surface on which the sensor is positioned and delivers back to each of the sensor cells a proportional intensity signal to light reflected from the surface of the mail item.

According to a second embodiment of the invention illustrated diagrammatically in FIG. 2, the weighing module 14 comprises a fixed optical reading assembly which, in conjunction with the local processing unit 22, enables automatic acquisition of the image of each of the mail items as they pass through this optical reading set. This assembly is advantageously arranged at the input of the module under the transport path of the mailpieces and is formed simply of a contact image sensor 20A (CIS: contact image sensor) identical to that described above and whose length is also intended to allow acquisition of images in A4 format, ie a maximum mail article width of about 216 mm.

In either of these two embodiments, the acquisition (digitization) of the image of a mail item is performed line by line from a start signal automatically given by the detection. a change in the intensity signal delivered by the sensor cells of the image sensor (a detector of the front of the article of mail could also have given similar information), the frequency of acquisition / reading of the signal being predetermined according to the desired resolution and the speed of movement of the mail items (an encoder secured to one of the movable rollers could also have given a similar synchronization information), so as to deliver successively, under the control of the local processing unit 22, a control signal and read signals of the intensity levels of the detection cells. The signals collected by the processing unit may be analog or digital depending on the nature of the image sensor and will therefore be digitized if necessary by an analog / digital converter 22A whose output is connected to an associated microprocessor circuit 22B if necessary (when the microprocessor does not integrate internal memory) with a RAM 22C at which the image of the mailpiece can be restored. In a preferred embodiment, the microprocessor circuit may be replaced by a wired logic circuit having its own internal clock such as a Field Programmable Gate Array (FPGA) or a programmable complex Iogic device (CPLD). In another embodiment, the local processing unit may form part of the general processing unit 18 of the franking module 16, the connection with the feeder / extraction or weighing modules then taking place through existing electrical links between these modules.

The measurement method implemented in the mail processing machine according to the invention can be described as follows. The acquisition of the image of the mail piece by the image sensor can be carried out in different ways depending on the type of image sensor used and more particularly according to the acquisition / reading (or sampling) frequency ) of the analog / digital converter used. Thus, with a sensor having a sampling frequency of 15 khz or higher, such as the X200 or XGD106AX circuits of the Japanese company Mitsubishi having an integrated analog / digital converter, it is possible to acquire a complete image of the article of mail with a resolution of 200 dpi for travel of these mail items up to 2 m / s. And from this complete image of the mail article, it is then easy to determine the width and length of this article of mail using the various algorithms known in the image processing as the so-called extraction segmentation contours implemented in the microprocessor circuit. On the other hand, when the use of the previous fast reading circuit is not conceivable, especially in low-end processing machines where cost issues are paramount, it is nevertheless possible to determine the dimensions of the article. of mail by acquiring not a complete picture of the mail item but only some vertical lines of that image. For example, with the C2R216 circuit of the Chinese company SHEC, it is possible to acquire up to 1 line / mm at a movement speed of 2 m / s (ie 229 lines for a C5 European format envelope). Thus, each vertical line (as long as the end of line signaling is not sent by the sensor) is digitized by an external analog / digital converter and for each detection cell the processing unit compares the intensity signal ( for an 8-bit converter, this signal is a gray level between 0 and 255) obtained with respect to a predetermined threshold pre-recorded in a register (advantageously at the level of the FPGA or the CPLD) of the local processing unit. If the value obtained is greater than the threshold, the corresponding pixel is considered to belong to the mail item and a counter (advantageously in the RAM memory) of the local processing unit is then incremented by one unit. If not, it is assumed to concern the transport path outside the mail item and the counter is not incremented or is then stopped at a value proportional to the width of the mail item if the count was been engaged. Indeed, the width of the mail item is deduced simply by dividing this value of the counter by the resolution of the image sensor, for example if 500 pixels have been recognized with a sensor having a resolution of 200 dpi ( 7.9 pixel / mm), a mailpiece width of 500 / 7.9 = 63 mm.

It will be noted that in order to constitute a more robust measurement, it may be envisaged to average the width obtained on several lines of the mail article. For this, the steps described above will be repeated at a predefined line interval (it is not necessary to acquire all the lines if one does not wish, as illustrated further, to determine the length of the article. mail, an acquisition every 50 lines can then suffice). This acquisition can be repeated until the end of the mail item is detected or until a predetermined number of lines are reached. For this, for each line acquired, the successive values of the width of the mail item will be stored in an array of the local processing unit, for example in internal registers or in the associated memory, and these width values stored in the table will then be averaged to give an average width. Applied to the line in its entirety, this threshold detection then makes it possible to determine whether this digitized line belongs or not to the article of mail and thus to determine the length of the article of mail. To do this, several vertical lines must be acquired at a predefined interval which must be sufficiently fine to measure the length of the mail item in a fairly precise manner. When a line of which at least part of its pixels has been acquired on the article of mail is detected (that is to say that at least X consecutive pixels greater than the threshold have been acquired), it is proceeded to the incrementation of a second counter and when a line contains only pixels acquired outside the envelope (that is to say that there is no more mail item under the sensor d the counter is stopped and the counter value corresponding to the number of lines counted on the mail piece is used to determine the length of the envelope according to the following formula: number of counted lines multiplied by the interval between lines. Thus, for example 229 lines counted with 1 line per mm will give a mail piece length of 229 x 1 = 229 mm.

Of course, various known image processing algorithms can be implemented in addition to this threshold detection to refine the result and make it more efficient, particularly in cases where the presence of characters printed on the mailpiece could have the effect of delivering for the corresponding pixels a level of gray similar to that of the transport path. Similarly, to ensure that a pixel has been acquired on the mail piece and it is not a parasitic pixel, when a first pixel of value greater than the predefined threshold is found, At least the next X adjacent pixels must also have values above this threshold to consider the pixel as belonging to the mail item. The same goes for pixels acquired outside the mail article. When a first pixel of value lower than the threshold is found, it is necessary that at least the following Y consecutive pixels also have values lower than the threshold to validate the acquisition.

FIG. 3 illustrates, for example, different gray levels obtained during the passage of a mail article 24 in front of the image sensor 20A. On curve 26, it is noted that the gray level of about 170 over the entire width of the mail item falls to about 5 outside of it. This change in gray level is found at the front and back of the mail article on the curve 28 which illustrates the gray levels obtained for the same detection cell as a function of the displacement of the mail item and therefore the number of lines counted. For either of these two curves, it can be seen that the setting of a gray level threshold of the order of half of the maximum threshold raised, for example to 80 will allow to achieve without ambiguity this detection of the change of gray level. It should be noted that the invention is not limited to the measurement of a mail piece width in A4 format. Indeed, the minimum acceptable format for a mail article is now the business card size is a width of 90 mm, it is possible by removing the optical reading assembly of the reference wall 30 of a predetermined distance, for example 70 mm, sufficient to recognize this type of mail to increase the width of mail piece to be measured. Thus, by placing the optical reading assembly not against the reference wall but at 70 mm from it, it becomes possible to measure mail items having widths of up to 286 mm instead of 216. mm. At the extreme, it may be envisaged to place two sensors one after the other (the signals obtained being multiplexed) and thus to allow measurements up to A3 format. Thus, the invention makes it possible to obtain a high measurement resolution on formats of mail items having a width of up to A3 with very low cost means requiring very little space.

Claims (15)

REVENDICATIONS1. Mail processing machine comprising: means (12, 14) for conveying to postage means (16) mail items each having a specified length and width, means (20) for acquiring an image of each of these mail items as they move through the machine, and. processing means (18; 22) for, from these successive images, determining the width of each of these mail items. Mail processing machine according to claim 1, characterized in that said means for acquiring an image comprise means for acquiring a vertical line of pixels of said image and that said processing means determines said width of the image. mail article by comparing the value of each of said pixels to a predetermined threshold. 3. Mail processing machine according to claim 1, characterized in that said processing means also determine the length of each of said mail items from these successive images. A mail processing machine according to claim 3, characterized in that said means for acquiring an image comprises means for acquiring a predetermined number of vertical lines of pixels of said image and that said processing means determines said length of the mail article by comparing the value of each of said pixels forming said vertical lines with a predetermined threshold value. A mail processing machine according to claim 1, characterized in that said image acquisition means comprises a linear image sensor (20A) disposed perpendicular to the direction of movement of said mail items. A mail processing machine according to claim 5, characterized in that said linear image sensor is vertically movable and moves in synchronism with at least one transport wheel of a supply module (12) of said mail processing machine. A mail processing machine according to claim 5, characterized in that said linear image sensor is fixed and mounted under the transport path of a weighing module (14) of said mail processing machine. The mail processing machine according to claim 5, characterized in that said linear image sensor is a contact image sensor formed of an integrated module having a line of adjacent semiconductor detection cells, a collimation optics and a lighting system allowing A4 scanning. 9. A method of measuring the dimensions of a mail item in a mail processing machine comprising the following steps: acquiring an image of each of these mail items as they move through the machine, and. from these successive images, determining the width of each of these mail items. 20 10. Method according to claim 9, characterized in that said step of acquiring an image of the mail article comprises acquiring a vertical line of pixels of this image and in that said processing step determines said width of the mail piece by comparing the value of each of said pixels with a predetermined threshold. 25 11. The method of claim 9 or claim 10, characterized in that it further comprises a step of determining the length of each of said mail items from these successive images. 12. The method according to claim 11, characterized in that said step of acquiring an image of the mail article comprises acquiring a predetermined number of vertical lines of pixels of said image and in that said processing step determines said length of the mail piece by comparing the value of each of said pixels forming said vertical lines with a predetermined threshold value. 13. Method according to claim 9, characterized in that said step of acquiring an image of the mail article is performed by a contact image sensor formed of an integrated module comprising a line of detection cells. adjacent semiconductor, collimation optics and illumination system allowing A4 scanning. The method according to claim 13, characterized in that to enable a larger format mail article to be digitized, said contact image sensor is moved away from a reference wall (30) by a distance predetermined amount corresponding to at most the smallest width of mailpiece to be processed. The method of claim 13, characterized in that to enable scanning of a larger size mail article, said contact image sensor is arranged in series with at least one other contact image sensor.