Abstract:
The method of processing postal items comprises the following steps: causing the postal items to advance in series past a camera ( 120 ) for the purpose of generating an image ( 1 ) of one face of each postal item, which face bears postal address information; filtering the image of a current postal item for the purpose of isolating, in the image, at least one region of interest (ROI) containing the address information; and sending the filtered image to an automatic recognition unit ( 130 ) for automatically recognizing postal addresses by means of OCR so as to extract the postal address from said filtered image and so as to direct the current postal item to a sorting outlet. In order to construct a filter mask, the method further comprises causing a card ( 20 ) of the “separator” type to advance past the camera ( 120 ), which card has a face on which said region of interest (ROI) is represented.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a 35 U.S.C. §371 National Phase Application from PCT/FR2007/051562, filed Jun. 29, 2007, and designating the United States, which claims the benefit of France Patent Application No. 0654225, filed Oct. 12, 2006. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to automatically processing batches of postal items such as letters, large-format flat items or “flats” (e.g. magazines or newspapers in plastic or paper wrappers), or indeed parcels. 
         [0004]    The invention relates more particularly to a method of processing postal items that consists in causing the postal items to advance in series past a camera for the purpose of generating an image of one face of each postal item, which face bears postal address information, in filtering the image of a current postal item for the purpose of isolating, in the image, at least one region of interest (ROI) containing the address information, and in sending the filtered image to an automatic recognition unit for automatically recognizing postal addresses by means of Optical Character Recognition (OCR) so as to extract the postal address from said filtered image and so as to direct the current postal item to a sorting outlet. 
         [0005]    2. Discussion of the Background Art 
         [0006]    OCR is a well-known image-processing technique in which images are recorded with suitable resolution and machine-recognizable symbols (in particular letters and numerals) are extracted from the images and are then evaluated. Modern OCR systems for automatically recognizing postal address information such as a postal delivery address can achieve processing throughputs of several tens of thousands of postal items per hour. However, the reliability of the recognition can vary considerably as a function of the writing style with which the address information is written on the postal items and also of the quantity of information appearing on the postal items. When the address information can be recognized automatically and unambiguously by OCR, the postal item corresponding to said address information can be directed automatically to a sorting outlet. Otherwise, the image of the postal item must be sent to a video coding system while the postal item itself waits to be sorted, which increases the processing costs for the postal operator. 
         [0007]    Frequently, for a batch of postal items (for bulk mailing), the delivery addresses on the postal items are located at the same place on the face of each of the postal items, but that face also bears other address information such as the address of the sender of the postal item. In which case, automatic recognition cannot succeed because multiple addresses are present on the face of each of the postal items. It is possible to superpose a filter mask on the image generated for each postal item by the camera, in order to isolate one or more regions of interest (ROIs) in the image of the postal item, in which region(s) the relevant postal address information (in particular the postal delivery information) is situated, thereby contributing to reducing the recognition error rate. 
         [0008]    After filtering, the image that is sent to the OCR automatic recognition unit is, for example, a blank (white-background) image (i.e. an image of the background of the mask) inside which appears, in a rectangle, only the delivery address block (i.e. a region of interest), e.g. in the form of gray-scale pixels of the original image generated by the camera. The filter mask can be more sophisticated in that it leaves visible, in gray scale, a plurality of distinct rectangular zones including postal address information. It is possible to provide ROI filtering that is different for different inlet lines of a sorting machine. 
         [0009]    3. Description of the Related Art 
         [0010]    Document U.S. Pat. No. 6,665,422 teaches using a video coding station for defining a region of interest. When a postal item image generated by the camera cannot be evaluated unambiguously by the OCR recognition unit, that image is displayed on the screen of a video coding station as superposed with a grid. The position in the image of the address block containing the address information is specified by the video coder which enters position data by using the grid, that position data then being delivered to the OCR recognition unit. That method of defining a region of interest can be implemented only for postal items processed in time-shifted manner. 
         [0011]    Patent Document EP 0 596 724 also discloses a method of scanning a document containing a plurality of pages, that method consisting in reading a code on a separator placed at the beginning of the document. That code indicates the region to be scanned or “region of interest”. Unfortunately, Patent Document EP 0 596 724 does not make it possible to perform real-time automatic sorting or merely to update the region of interest. 
       SUMMARY OF THE INVENTION 
       [0012]    An object of the invention is to propose a method of defining at least one region of interest, which method can be implemented while the postal items are being automatically sorted in real time, in particular a method as defined above in which a filter mask is used to deliver a filtered image to the OCR recognition unit but which is improved so that the mask is easier to construct. 
         [0013]    Another object of the invention is to propose such a method that makes it possible to avoid manipulation errors made by the machine operators during activation of the image filtering, and in particular that avoids having the filter mask parameters input manually on a keyboard by the machine operators. 
         [0014]    Another object of the invention is to propose such a method that makes it possible to change the characteristics of the filter mask while a stream of postal items is flowing through the machine, without interrupting the inlet flow into the machine. 
         [0015]    To these ends, the invention provides a method of processing postal items, which method consists in causing the postal items to advance in series past a camera for the purpose of generating an image of one face of each postal item, which face bears postal address information, in filtering the image of a current postal item for the purpose of isolating, in the image, at least one region of interest containing the address information, and in sending the filtered image to an automatic recognition unit for automatically recognizing postal addresses by means of OCR so as to extract the postal address from said filtered image and so as to direct the current postal item to a sorting outlet, said method being characterized in that it further consists in causing a card of the “separator” type to advance past the camera, which card has a face on which the boundary of said region of interest is represented graphically, so as to construct a filter mask. 
         [0016]    Advantageously, in accordance with the invention, a separator on which the boundary of the region of interest is represented graphically makes it unnecessary to use a memory or a database containing the postal item formats, and thus unnecessary to update such a database. Furthermore, the method is not interrupted due to accessing such a memory. Finally, the senders of the postal items can themselves print out and update their separators with the regions of interest positioned correctly. 
         [0017]    In accordance with the invention, a card of the “separator” type having a face on which one or more regions of interest are represented graphically is caused to advance past the camera in order to construct a filter mask. The “filter mask” is used herein broadly to designate information data for performing graphic filtering in an image with one or more portions of the image being masked. With the method of the invention, in order to change the filter parameters for filtering the images, it is thus merely necessary to insert a new “filter card” into the inlet of the sorting machine, which new card represents the new regions of interest, at the head of the batch of postal items to whose images the new image filtering is to be applied. The new filtering parameters can consist both in activating the filtering and also in deactivating the filtering depending on the manner in which the region(s) of interest is/are represented on the “filter card”. A plurality of different “filter cards” can easily be inserted successively by the machine operator as the postal items to be sorted are fed into the inlet of the machine. 
         [0018]    In a particular implementation of the method of the invention, a portion of the outline of said region of interest is represented by a rectangle. 
         [0019]    In a particular implementation of the method of the invention, a portion of the outline of said region of interest is represented by two corners of a rectangle. 
         [0020]    The method of the invention for processing postal items can, in particular, present the following features:
       a search is made in the image generated by the camera for the presence of a specific code indicating that said image is the image of a card of the “separator” type on which at least one region of interest is represented;   if the presence of said specific code is detected in said image, a search is made in said image for a rectangular outline that surrounds said specific code;   a bar code is used as the specific code;   it is determined whether said specific code identifies the zone lying within the rectangle as being a zone to be included in or a zone to be excluded from the filter mask; and   it is determined whether said zone has a relative position or an absolute position in the image.       
 
         [0026]    The invention also provides a postal sorting machine including a camera for generating an image of one face of a postal item, which face bears postal address information, and an automatic recognition unit for automatically recognizing postal addresses by means of OCR, which unit extracts the address information from said image so as to direct the postal item automatically to a sorting outlet corresponding to said postal address, said postal sorting machine being characterized in that it further includes an image processing unit which is interposed between the camera and the recognition unit, and which is arranged so that:
       it detects the presence of a specific code in the current image generated by the camera, which code indicates that said image is the image of a “separator-type”, card on which the boundary of at least one region of interest is represented graphically; and   in response to such detection, said image processing unit constructs, in a memory of the machine, a filter mask corresponding to said region of interest, applies filtering to an image subsequent to the current image generated by the camera by superposing said filter mask on the subsequent image so as to form a filtered image in which said region of interest is isolated, and sends said filtered image to the recognition unit.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The method and the machine of the invention can be better understood on reading the following description of an implementation and of an embodiment that are shown in the drawings, in which: 
           [0030]      FIG. 1  is a diagrammatic view of a sorting machine for implementing the method of the invention; 
           [0031]      FIG. 2  is a view of a “filter card” of the invention; and 
           [0032]      FIG. 3  is a flow chart showing the various steps of the method of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]      FIG. 1  is a highly diagrammatic view of a postal item sorting machine  100  specially arranged for implementing the method of the invention. 
         [0034]    The postal item sorting machine  100  includes an unstacker device  110  for unstacking postal items and putting them in series, which unstacker device takes the postal items from a storage magazine  111  of an inlet line where they are, for example, disposed on edge in a stack. At the outlet of the device  110 , the series of on-edge postal items are successively brought past a camera  120  which takes an image  1  of one face of each postal item. The postal items are then conveyed through a time-delay zone  121  before being directed to sorting outlets  160 . 
         [0035]    While the postal items are flowing through the time-delay zone  121 , the images  1  of the postal items are sent successively to an image processor unit  125  which can apply filtering to said successive images so as to generate filtered images such as  3  which are sent to an OCR postal address recognition unit  130  that extracts the postal address of the postal item from an image  3  and evaluates it so as to control the machine  100  in a manner such as to direct said postal item to a sorting outlet that corresponds to its postal address. 
         [0036]    The OCR recognition unit  130  is generally also connected to a video coder system represented by the block  170  for time-shifted recognition of the postal address information on the postal items. 
         [0037]    In the filtered image  3 , an address information block, defined in this example by a rectangle, has been isolated from the rest of the image (shown by hatching and that can be in form of a white background) by superposition with a filter mask. The filtering operation that consists in superposing a filter mask on a postal item image is well known to the person skilled in the art and is not described in any further detail below. 
         [0038]    In order to activate filtering of the invention on a region of interest in the unit  125 , a card  20  of the “postal item separator” type having one face on which the region of interest is represented is inserted into the inlet of the machine  100 , and more particularly into the postal item feed magazine  111 . Said card  20  is therefore unstacked and presented facing the camera  120  so that an image is taken that, instead of bearing address information, bears a representation of a region of interest. 
         [0039]    For the purpose of processing batches of postal items with prior filtering of a region of interest in each of the postal item images, the machine operator loads the postal items in a stack into the feed magazine  111 , the first postal item in the stack however being preceded by the card  20  representing said region of interest. If the filtering is to be deactivated/modified in the unit  125  at the end of processing of the batch of postal items, the machine operator disposes another appropriate card  20  at the end of the stack of postal items. It is conceivable for the filtering also to be deactivated by a specific operator command from the workstation on the sorting machine. 
         [0040]    Postal item separators are already used in sorting outlets for separating postal items belonging to different delivery rounds or “postman&#39;s walks”. Said card  20  that serves to indicate a region of interest to the machine for automatic recognition purposes is in the form of a separator can be made of printable card reinforced with a plastics material. The card  20  can have the same size as a postal item to be processed in the machine  100 . 
         [0041]    In  FIG. 2 , the card  20  identifies two distinct regions of interest. In particular, the image of the card  20  shows two first bar codes  2 A 1  and one other bar code  2 A 2 , the bar codes being, for example “128” bar codes of French Standard NF EN799, two of the three bar codes being surrounded by the outlines of respective rectangles  2 B which correspond to two regions of interest in this example. 
         [0042]    By way of example, and in order to enable the invention to be well understood, both of the bar codes  2 A 1  and  2 A 2  are specific codes that are recognizable by the processor unit  125 . For example, the codes  2 A are designed to indicate that the zone within the rectangular outline  2 B that surrounds the specific bar code  2 A 1  is a zone to be included/isolated in the filtered image (i.e. said zone is not a filter zone in the filter mask) whereas the specific code  2 A 2  is designed to indicate that the zone that surrounds it, within the outline of the image in this example, is a zone to be excluded/filtered out in white in the filtered image (i.e. a filter zone in the filter mask). 
         [0043]    A zone identified by a specific code  2 A 1  (inclusion code) is thus a non-filter zone, whereas a zone identified by a specific code  2 A 2  is a filter zone in the image to be filtered. 
         [0044]    In practice, in the example shown in  FIG. 2 , the filter mask of the card  20  defines two distinct rectangular regions of interest (in the middle of and at the top right of the image) that correspond respectively to the region in which a delivery address is normally situated and to the region in which a postage mark is normally situated. 
         [0045]    The size of the rectangular outlines  2 B can be about 40 millimeters (mm) long and about 20 mm high. This representation by rectangles with associated specific bar codes thus makes it possible to define one or more distinct regions of interest. If a specific bar code such as  2 A 2  is associated with a zone to be excluded that overlaps a zone  2 A to be included that is associated with another specific bar code such as  2 A 1 , it is possible to make provision in the unit  125  for the filter mask to be constructed in a manner such that said zone to be included prevails over the zone to be excluded in the filtered image. 
         [0046]    In addition, as shown in  FIG. 2 , in each of two corners of the rectangle in the middle of the image  2  and in one corner of the rectangle at the top right of the image  2 , a sort of black triangle can be used as a symbol to identify in the unit  125  that the position of the rectangle in question is a relative position in the image (absence of such a symbol in a corner of the rectangle indicating that the position of the outline is an absolute position in the image). The term “relative position” is used to mean that the size of the outline of the rectangle in the filter mask must be dimensioned to the size of the image of the postal item to be filtered. It is also possible to use a convention whereby, depending on whether one or two corners of the outline are marked with such a symbol, the dimensioning acts on one side of the outline only or on both sides of the outline. 
         [0047]    The filter card represented by  20  in  FIG. 1  corresponding to the image of  FIG. 2  can be made on a conventional printer by printing the outlines of the rectangles and the bar codes in black ink on a blank card that is completely white, for example. In order to deactivate image filtering completely, it is conceivable to use a card that is completely white and on which only a bar code such as  2 A 1  is printed, indicating that the zone surrounding it is a zone to be included in the filter mask. 
         [0048]      FIG. 3  shows various processing steps performed in the unit  125 . 
         [0049]    In step  30 , the unit  125  receives an image  1  generated by the camera  120 . 
         [0050]    In step  31 , image analysis is used to search the image  1  for a specific code, such as the bar codes  2 A, indicating that the image is the image of a “filter” card representing a region of interest (ROI). 
         [0051]    If, in step  32 , the presence of said specific code has been identified (i.e. if a card  20  has been inserted into the magazine  111  of the machine  100  and brought by the device  110  past the camera  120 ), image analysis is used in step  33  to perform a search for identifying a frame (outline) of one or more rectangles. Depending on the results of said search, at least one region of interest is determined as explained above, and a filter mask is constructed in a memory of the unit  125 . The image of the “filter” card is not delivered to the OCR recognition unit  130 , and a special command (analogous to a “separator” command) is returned to the sorting machine by the unit  125 , thereby causing the card  20  to be directed to a sorting outlet  161  that is, for example, reserved for reject postal items. 
         [0052]    If, in step  32 , the presence of said specific code is not identified in the image, the processing continues, in step  34 , with checking for a parameter indicating activation or deactivation of the ROI filter function (activation/deactivation of the filter mask recorded in the memory). If the filter function is activated at  34 , the process continues, in step  35 , with an operation of superposing the filter mask on the image  1  received at the inlet of the unit  125  so as to generate a filtered image such as the image  3  in  FIG. 3 . In the image  3 , the hatched zone corresponds to a white image background. Said filtered image  3  is sent to the OCR recognition unit  130 . 
         [0053]    When, in step  34 , the filtering is deactivated, the input image  2  is directly sent by the processing unit  125  to the OCR recognition unit  130 . 
         [0054]    The processing unit  125  which is interposed between the camera  120  and the unit  130  can be an integral part of the programmed circuits of the camera  120 . 
         [0055]    Following on from the invention, it is possible to make provision for the image of a “filter” card that is detected by the unit  125  to be displayed on a display screen for the purposes of being checked by the machine operator. In order to reinforce the manipulation error checking procedures, it is also possible, in the specific codes  2 A of a “filter” card  20 , to encode the code of the sorting machine on which the filter card is used, and, in step  33 , to check that the machine number resulting from the code  2 A is indeed the code of the machine on which the processing unit  125  is installed. 
         [0056]    The method of the invention for activating/modifying/deactivating an ROI filter function on the images of the postal items offers the advantage of having no repercussions on operation of the OCR address-recognition unit  130 .