Abstract:
A document-examining apparatus is provided for automatically examining the authenticity elements of secured documents. It includes a compound slide which can be moved in the X and Y directions and on which the components required to evaluate the distinguishing authenticity features are mounted. The X slide of the compound slide is mounted on a Y slide. A first group of evaluating units for evaluating diffraction elements on a document is disposed on the X slide. A second group of evaluating components, for example, for evaluating text, an IR field and/or a photographic field, may be mounted on the Y slide. In addition, a source of UV radiation may be provided for examining distinguishing fluorescence features of a document, the fluorescence being evaluated by a stationary evaluating unit or by the evaluating unit on the X slide.

Description:
This application is a continuation of international application Ser. No. PCT/EPO1/05990, filed May 25, 2001, which was published in German. 
    
    
     This invention relates to apparatus for automatically examining documents for the purpose of determining authenticity. 
     BACKGROUND OF THE INVENTION 
     There are many different types of documents and things which are subject to counterfeiting or forgery, and many different techniques and devices have been developed for determining the authenticity of a document or thing. By way of example only, such documents include bank notes, identification papers, passports, drivers licenses, visas, admission tickets and stock certificates. As used herein, the term “secured document” includes any document or thing which is provided with a distinguishing authenticity element (whether printed or not) which can be used to authenticate, identify or classify the document. The term “authentication element” is intended to refer to any “device” which may be printed on, or otherwise attached to, a secured document for the purpose of authenticating the document or for the purpose of determining its value and/or type or any other characteristic. Likewise, “authenticity” is meant to encompass value, type or other characteristic of a secured document as well as the genuineness of the document. 
     There are machines which automatically examine authentication elements on a multiplicity of secured documents. In one known machine, the secured document is supported on a transparent supporting surface and illuminated from below by a fixed light source. The reflected image is captured by a stationary camera (typically, one or more matrix cameras) and the image evaluated with appropriate software. Such devices have relatively low resolution and, though suitable for reading text within the document, are not suitable for reading a two dimensional bar code or authenticity elements which are based on diffraction or which are hidden steganographically in parts of the image. 
     Authentication elements are known which operate on principles of light diffraction. With diffraction systems, a light source (typically a laser) illuminates a diffraction element (e.g., a hologram) to produce a diffraction pattern that can be sensed and evaluated to determine authenticity. In known devices of this type, the laser and associated evaluating unit are housed in a hand held unit which can be placed by hand on the authenticity element which can be recognized with the naked eye. Heretofore, such authenticity evaluating units have not been incorporated into machines which are used for automatically examining documents. 
     Automatic document-examining machines are known which include a flat bed scanner having a slide movable in the Y direction on which an illuminating device and camera are mounted. The camera records the image produced by the illuminated document and evaluates it; however, such flat bed scanners are not suitable for automatically examining authenticity elements which are based on diffraction principals wherein laser illumination is required. Moreover, flatbed scanners are not suitable for identifying special elements on a document which must be illuminated with different sources of illumination. 
     It is a principal object of the invention to provide a document-examining machine of the type described wherein distinguishing authenticity elements can be examined rapidly and accurately. 
     A more specific object is to provide a document-examining machine which can be used to automatically examine authenticity elements based on diffraction principals reliably and satisfactorily. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, a machine for automatically examining secured documents includes a compound slide which is movable in both the X and Y directions. The components required to evaluate the authenticity elements are disposed on the compound slide. The compound slide includes a slide which is movable in the X direction mounted on a slide which is movable in the Y direction. The units for evaluating the diffraction pattern are mounted on the X slide whereas the other components used for evaluating text (for example) are mounted on the Y slide. 
     With this arrangement, it is possible to identify the authenticity element in situ directly with high resolution and accuracy. Because the evaluating unit can be positioned in both X and Y directions, it is possible to compensate for errors in the position of the authenticity element on the secured document. For example, if a document has been produced with the authenticity element displaced by several millimeters, the XY slide can be positioned so that the evaluating unit is directly below the authenticity element. 
     Preferably, the unit for evaluating the diffraction patterns consists of a laser and appropriate optical evaluating system, all of which are mounted on the X slide which can be moved in both X and Y directions. With this arrangement, it is possible to move the entire evaluation unit (i.e. the laser and associated optical unit) and position it accurately under the distinguishing authenticity element of the secured document. Other optical evaluating components, for example, used to evaluate text, an IR field and/or a photographic field are preferably mounted on the Y slide and, therefore, can be moved only in the Y direction. These components can be used to scan the document accurately over its entire width on a line by line basis with a single scan in the Y direction. 
     It is further contemplated that an illuminating unit may be mounted on the Y slide although this is not essential because one or more illumination units may also be disposed outside of the XY slide in order to illuminate the document. However, if the illuminating unit is mounted on the slide and consists of at least one illuminating line, when the Y slide is scanned relative to the document, the illuminating line produces a scanning line on the document over the entire width of the document. This scanning line may be directed by an appropriate mirror system onto an OCR matrix camera for evaluation. 
     As a further embellishment of the invention, the document-examining device may include a stationary evaluating unit for distinguishing fluorescent features of the document. For this purpose, a stationary camera mounted in the housing of the device is directed at a mirror which images the supporting surface on which the document is resting. The supporting surface is illuminated in the UV range with a suitable source of UV illumination so that the authenticity elements of the document are stimulated to fluorescence and emit light which is directed by the mirror onto the stationary camera. This evaluating unit is thus completely independent of the X-Y slide. 
     In a different version of this evaluating unit, the stationary UV camera is omitted; instead, the camera used for the laser evaluation on the X slide is also used at the same time for evaluating the UV image. 
     Two cameras, separated from one another, can also be mounted on the X slide, one of which is suitable for the laser evaluation of diffraction elements, while the other camera is intended for evaluating the UV image. 
     The invention is not limited to evaluation in the UV range; this depends, in particular, on the nature of the filters used and on the type of illumination employed. All evaluations can also take place in a different region of the spectrum; in particular, instead of the UV filters, it is also possible to use polarization filters. Completely different wavelength regions can be used as well. For example, the wavelength range of the NIR (near infrared) or any other wavelength range can be used. Any mention of a UV evaluation in this specification is to be regarded only as exemplary. 
     The use of an X-Y slide with the laser evaluating unit mounted in the X slide has the significant advantage that the laser unit is well protected against a loss of adjustment. 
     It is possible to use a stationary laser which beams onto an opposing mirror, the reflection of which is imaged on an evaluating unit disposed in a slide so that it can be moved. This, however, has the disadvantage that the beam path between the stationary laser and the oppositely disposed mirror is long, so that the arrangement as a whole loses adjustment easily. Such a device is very sensitive to shocks which cause it to lose adjustment, after which it can only be adjusted with difficulty. 
     In accordance with the invention, the entire evaluating unit (laser, mirror and associated camera with lens) is disposed in a very tight space on an (inner) slide, which can be moved in X and Y directions. As a result, the whole unit is protected against shocks, because the beam path between the laser unit and the evaluating unit is short. 
     During transport, the whole X-Y slide can easily be secured (locked), as a result of which the guides, in which the X-Y slide is guided, are also protected and secured against deflection. 
     The invention also relates to the kinematic reversal of an X-Y slide. The slide movable in the X direction may be an inner slide, and the slide movable in the Y direction an outer slide which can be moved along the document. In a kinematic reversal, the inner slide can be moved in the Y direction and the outer slide in the X direction. 
     The aforementioned X-Y slide or Y-X slide can also be replaced by other position systems, which can be positioned in two planes. Provisions are therefore made that all the evaluating components can be moved freely in space in two directions perpendicular to one another. This can be accomplished by spindle drives, by electric motor drives, or by electromagnetic drives. Such systems, which can be positioned freely in the X-Y plane, are known. They employ hydraulic or pneumatic cylinders, or spindles driven by an electric motor or the like. 
    
    
     
       THE DRAWINGS 
         FIG. 1  diagrammatically shows a section through a document-examining device according to a preferred embodiment of the invention; 
         FIG. 2  shows a side view of a laser evaluating unit; 
         FIG. 3  shows a section through the device, further details being shown; 
         FIG. 4  shows a separate representation of the X slide with its driving mechanism; 
         FIG. 5  shows a side view of the Y slide; and 
         FIG. 6  shows a plan view of the device of  FIG. 3  with the X slide in two different positions. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , the housing  1  of a document-examining device is shown. The housing is a desk-like construction and has a front plate  2  which is inclined at an angle  4  to the horizontal and within which a transparent supporting surface  3  (for example, glass) is disposed. The document to be examined is placed on the supporting surface and pressed against it with a defined pressure so that the document surface which is to be examined is visible from the underside of the supporting surface  3 . 
     According to the invention, an X-Y slide  7 ,  8  is movably mounted in slide guides which are described below. The Y slide  7  is movable in the Y direction of arrow  5  and the X slide is movable in the direction of arrow  6  (namely, transverse to the plane of the drawing of FIG.  1 ). 
     It is preferred that the outer Y slide  7  carries the less sensitive evaluating components comprising an illuminating unit  14  which is inclined at an angle to the direction of the plane of front plate  2  in front of a focusing lens  15 . The illuminating unit  14  and focusing lens are preferably linear devices with the light from illuminating unit  14  focused by lens  15  onto the underside of the document resting on the supporting surface  3 . Preferably, the illuminating unit  14  consists of a linear array of LEDs (see  FIG. 6 ) and produce white light. However, other illuminating units may also be used, such as an illuminating unit in which LEDs are provided, one portion of which radiates white light and the other IR light. Several illuminating units  14  may be disposed side by side or above one another, and each illuminating unit may generate a separate spectrum or a mixed spectrum. 
     The light reflected by the illuminating unit from the underside of the document is passed over the beam path  13  onto a tilted mirror  12  and directed through a lens  11  onto a line camera  10 , which is suitable for evaluating the text of a document or other image information or hidden information, which, for example, can be read only in the NIR range. 
     A signal processor in the shape of a plate  9  evaluates the images received by camera  10 , and is fastened to the Y slide  7 . This arrangement ensures that the information paths and the cable lengths are short; therefore, the arrangement as a whole is not highly susceptible to interference. 
     By comparing  FIGS. 1 and 3 , it can be seen that the direction of the beam path  16  may differ. In  FIG. 1 , the beam path  16  is inclined towards the front in the direction of the supporting surface  3 , and in  FIG. 3  it is inclined towards the rear. 
     The arrangement of an inclined beam path  16  at an angle to the supporting surface  3  is advantageous. Initially, the positions of the distinguishing diffraction features, which are to be detected with the laser evaluating unit, can be located roughly on the document during the scanning of the document. In other words, the position of the distinguishing diffraction features are initially noted roughly with the line camera  10  while the surface of the document is being scanned, and verified later with the laser evaluating component mounted on the X slide. 
     It is preferred that the actual verification of the distinguishing diffraction feature is carried out using the components mounted on the X slide  8 . These components consist of a laser  21  which produces a beam  22  ( FIG. 2 ) which is reflected by a tilted mirror  20  as a beam  23  onto the surface of the document to be examined. 
     It is assumed here that the X-Y slide is positioned precisely below the distinguishing diffraction feature which is to be examined; that is, the X-Y slide has been moved into a precisely fixed X-Y position.  FIG. 1  shows only the basic position. In the evaluating position, the X-Y slide is moved to a precisely fixed position which is suitable for evaluating the distinguishing diffraction feature. 
     The reflected image produced by the distinguishing diffraction feature (i.e., the diffraction pattern) is projected onto a screen, for example, a matt disk  19 , forming a diffraction pattern  49  which is viewed through the matt disk  19  from below through a lens  18  within a fixed angle  24  of an OCR matrix camera  17 , where it is evaluated. Thus, the entire evaluating unit is a compact unit disposed in a tight space in the X slide  8 , and does not easily lose adjustment. U.S. patent application Ser. No. 10/373,884 entitled “Device for Evaluating Diffractive Authenticity Features”, filed on Nov. 22, 2002 discloses a device for evaluating a diffraction pattern which is projected onto a matt disk, and that application is hereby incorporated by reference into this specification. 
     The UV evaluating unit is next described. It is used for evaluating fluorescing distinguishing authenticity features on the surface of a document. 
     The arrangement as a whole is oriented towards viewing in UV light. A UV flash  26  is equipped with a filter disk  27  which directs light with a high proportion of UV in the direction of arrow  30  onto the surface of the document. The light excites the surface of the document with fluorescing threads which light up characteristically. The light reflected by the document on surface  3  is guided between the limiting beam paths  32 ,  33  onto the mirror  25 , imaged from there through a lens  28  onto a camera  29 , and detected by a CCD chip which is situated there. 
     A UV filter, which blocks UV light, may be placed in front of the lens  28  so that only light from outside of the UV range is detected by the camera. This prevents the UV flash  26  from “blinding” the camera  29 . 
     The mechanical components of the arrangement are described in greater detail with reference to  FIGS. 3  to  6 . 
     As shown in  FIGS. 3 and 6 , two elongated guide rails  35  aligned in the Y direction, are mounted parallel to one another and anchored firmly in the housing  1  by supports  39 . Two cylindrical bushings  48  ( FIG. 6 ) attached to the Y slide  7  slide on the guide rails  35 . The Y slide is thus free to move in a controlled manner in the Y direction as indicated by arrows  5 . A stepper motor  34  which is firmly anchored in the housing  1  drives Y slide  7  by means of a cogged belt  37  which engages the motor drive shaft  36  and passes around a diverting pulley  40 . One side of the cogged belt is connected to the Y slide  7 . In  FIG. 6 , the connection between the endless belt  37 , drive shaft  36  and pulley  40  is shown diagrammatically, the actual arrangement being conventional with drive shaft  36  including suitable means for engaging the belt  37  so that rotation of the belt will drive the Y slide  7  in the directions of arrow  5  (FIG.  6 ). These elements are best shown in  FIG. 3  although, for purposes of clarity, belt  37  is not shown in engagement with pulley  40 . 
     The invention is not limited to an upper guide with upper, parallel guide rails  35 ; other guiding elements can also be used, such as lower guide rails  35 . Instead of four guide bushings  48 , more or fewer guide bushings can be used. Indeed, the specific details of the XY slide and the mechanism for controlling its movement form no part of this invention. 
     A housing  38  is mounted underneath the Y slide. The line camera  10  and the lens  11  are secured in housing  38  so that they can be exchanged easily, and adjusted separately from one another. In other words, because it is mounted in housing  38 , camera  10  can be adjusted accurately in the plant with respect to the lens  11  and, later on, the housing  38  can be adjusted accurately with respect to the tilting mirror  12  which is positioned outside of the housing. 
     The X slide  8  is mounted on the Y slide so that it can be moved perpendicularly to the plane of the drawing of FIG.  3 . The X slide  8  moves on a tubular guide  41  on its left side and a slideway  50  on its right side on which the Y slide is seated with a slide block. The tubular guide  41  is secured by two supports  46 , which are spaced from one another in the Y slide, as shown in FIG.  5 . 
     For adjusting the end position of the X slide  8  in the Y slide  7 , two limit switches  42 , which are also shown in  FIGS. 4 and 5 , are positioned at a distance from one another. The X and Y axes thus each have two limit switches. 
     The driving motor  43  for the X slide is fastened in the Y slide  7  and drives the X slide  8  in the direction of arrow  6  by means of its drive shaft  44 , a cogged belt  45 , and a pulley  47  supported in the Y slide. The arrangement of cogged belt  45 , drive shaft  44  and pulley  47  is best shown in  FIG. 5  wherein belt  45  is shown schematically. For purposes of clarity, belt  45  is only partially illustrated in FIG.  6 . Belt  45 , of course, can be connected to X-slide  8  in any suitable fashion and the connecting means is not shown in the drawings. The plan view ( FIG. 6 ) shows that the X slide  8  can be moved between two different end positions, the second end position of the X slide being indicated by  8 ′. 
     
       
         
               
               
             
           
               
                   
                   
               
               
                   
                 List of Reference Symbols 
               
               
                   
                   
               
             
             
               
                   
                  1. housing 
               
               
                   
                   2. front plate 
               
               
                   
                   3. supporting surface 
               
               
                   
                   4. angle 
               
               
                   
                   5. Y direction 
               
               
                   
                   6. X direction 
               
               
                   
                   7. Y slide 
               
               
                   
                   8. X slide 
               
               
                   
                   9. signal processing plate 
               
               
                   
                 10. line camera 
               
               
                   
                 11. lens 
               
               
                   
                 12. tilting mirror 
               
               
                   
                 13. beam path 
               
               
                   
                 14. illuminating unit 
               
               
                   
                 15. focusing lens 
               
               
                   
                 16. beam path (illumination) 
               
               
                   
                 17. OCR matrix camera 
               
               
                   
                 18. lens 
               
               
                   
                 19. matt disk 
               
               
                   
                 20. tilting mirror 
               
               
                   
                 21. laser 
               
               
                   
                 22. beam path 
               
               
                   
                 23. beam path 
               
               
                   
                 24. solid angle 
               
               
                   
                 25. tilting mirror 
               
               
                   
                 26. UV flash 
               
               
                   
                 27. filter disk 
               
               
                   
                 28. lens 
               
               
                   
                 29. matrix camera 
               
               
                   
                 30. direction of arrow 
               
               
                   
                 31. image 
               
               
                   
                 32. beam path 
               
               
                   
                 33. beam path 
               
               
                   
                 34. stepper motor 
               
               
                   
                 35. guide rail 
               
               
                   
                 36. drive shaft 
               
               
                   
                 37. cogged belt 
               
               
                   
                 38. housing 
               
               
                   
                 39. support (Y) 
               
               
                   
                 40. diverting pulley 
               
               
                   
                 41. tubular guide 
               
               
                   
                 42. limit switch 
               
               
                   
                 43. motor (X) 
               
               
                   
                 44. drive shaft 
               
               
                   
                 45. cogged belt 
               
               
                   
                 46. support (X) 
               
               
                   
                 47. diverting pulley (X) 
               
               
                   
                 48. spherical bushing (Y) 
               
               
                   
                 49. diffraction pattern 
               
               
                   
                 50. slideway