Device for evaluating authenticity features that have a diffraction structure

Description of the invention

The subject of the invention is an authentication device with a diffractive structure.

Such a device is known, for example, from WO 98/55963. The document to be checked is placed there on the glass plate and the diffractive structures to be recognized are placed on the document. To recognize these diffractive structures, a laser is used, the beam of which reaches the diffractive structure placed on the surface of the document, which characteristically deflects and reflects the beam in the form of a pattern. The diffraction pattern thus produced is projected onto photodiodes with a fixed fixed position in the housing. In the housing, they are located in places where the diffraction pattern is expected. Depending on whether the photodiode perceives a diffraction pattern or not, it is determined that the document is authentic.

A drawback of the known device, however, is that the photodiodes have to be placed in the document inspection device in a fixed, predetermined position, and it is assumed that the photodiodes will pick up the diffraction pattern at exactly this point. However, if the diffraction pattern on the surface of the document is slightly shifted or altered, or a different type of diffractive structure is given in another document, they are not perceived by photodiodes placed at fixed, predetermined positions. Thereby, there is a drawback that the known device is only applicable to a limited extent, since it is generally only suitable for one type of document.

While WO 98/55963 also describes that photodiodes can be arranged in a matrix to receive a wider range of diffraction patterns, the recognition of different diffraction patterns at different locations of different intensity using photodiodes with fixed, fixed positions is not without difficulties.

The second disadvantage of photodiodes is the very low resolution which lags far behind the very high resolution of matrix scan cameras or line scan cameras having CCD photosensitive sensing devices or CMOS sensing devices and therefore are not suitable for small, spaced authenticity features. .

The object of the invention is to improve a device of the above-mentioned type in this way, so that the authenticity features with diffractive structures can be recognized on a document with a substantially greater variety and that therefore the authentication of the document is independent of where the authenticity features with diffractive structures are placed on the document.

According to the invention, a device for recognizing the authenticity features of a diffractive structure (s) on a document which is located on the surface to be checked, with an illumination source which radiates the authenticity feature to be checked, the device having a recognition module on which it is to be checked. projected radius deflected by the authenticity feature, with a matte glass onto which the derived diffraction patterns and a camera are directed, which records a diffraction image reproduced on a frosted glass, characterized in that the frosted glass is slidably mounted in the device, and a stationary deflection device is mounted on it, by means of which the rays of the illumination source are deflected into rays that fall on the diffractive structure.

The advantage of the proposed device is, therefore, that no more precisely determined, and hence defined locations for, the incidence of the diffraction patterns on the test surface are foreseen, but that where the diffraction patterns fall is arbitrary.

Preferably, the camera recording the diffraction image reproduced on the frosted glass is a matrix-scan camera or a line-scan camera.

According to a further feature of the invention, the tilting device extends over the entire width of the frosted pane.

Preferably, the deviation device is a mirror.

According to a further feature of the invention, the camera is placed under a frosted glass pane.

According to another feature of the invention, the frosted pane is divided into sub-areas and the recognition module is assigned to one sub-area.

Preferably, the illumination source is connected directly to the frosted pane.

According to yet another feature of the invention, the illumination source is movable.

PL 198 952 B1

Further according to the invention, the illumination source is fixedly mounted on the housing, and the device has a pivoting pivot mirror on which the rays of the illumination source are directed.

Preferably, finally, the illumination source is a laser.

The camera tracks the entire projection surface and recognizes the characteristic diffraction pattern that develops there. Recognition of this diffraction pattern is thus a measure of the authenticity of the document. Thereby, there is the advantage that the photosensitive sensor devices no longer have to be positioned at predetermined locations on the projection surface, but there is complete freedom in recognizing the most diverse, also variable, diffraction patterns, since only the projection of the diffraction pattern onto the projection surface is checked with the camera.

As a result, different structures with different characteristics and appearing at different places on the document can be checked simultaneously or sequentially, since only the diffraction pattern projected by the diffraction structure onto the projection surface is always checked with the camera.

The term "projecting surface" is broadly understood. A frosted glass on which diffraction patterns are projected can be used as the projection surface, with a camera placed under the frosted glass which recognizes the diffraction patterns on the frosted glass.

The camera can image and recognize partial areas of the frosted glass or the entire surface of the frosted glass in just one work cycle.

The diffraction image can also be projected directly onto the photosensitive sensing devices of the recognition camera. In another embodiment of the present invention, it is possible to provide for the complete avoidance of frosted glass and to provide directly as the projection surface the image field of the matrix recognition chip or the line recognition chip, this chip being designed, for example, as a CCD chip or as a CMOS chip. This means that the diffraction image is projected directly onto the recognition surface of the respective camera with an electron beam profiled by a matrix or by lines, consisting of separate microfibers.

In the case of separation by the space of the camera and the frosted pane, it remains unresolved and within the scope of protection of the present invention whether the camera passes together with the matte pane moving in this case, or in the case of a fixed camera, only the frosted pane is moved. In the variant where the frosted glass is dispensed with and the diffraction image is projected directly onto the photosensitive sensor devices of the camera, it is envisaged that the camera travels together with the light source or is permanently attached to the housing.

Besides, for recognizing a diffractive structure in the document, there are many different embodiments which are included in the invention.

Thus, the laser provided to illuminate the diffractive structure in the document is made to be slidable, for example only in the X direction, but is stationary in the Y direction.

In another embodiment, the laser may be immobilized, for example in a housing, and may not itself be pivotable, the laser beams being directed onto a rotating mirror, the rotating mirror being pivotable within a certain angular range. Then the laser beam deflected by the rotating mirror is directed by means of a suitable telecentric mirror permanently fixed in the housing onto the diffractive structure in the document or document.

In both variants, the frosted glass may be slidable in the Y direction (in the scanning direction), and a deflecting mirror may be permanently attached to the frosted glass, so that the laser beam is guided by a mirror fixed on the matted sliding glass on the the stationary diffractive structure in the document.

What is important in this embodiment variant is that the mirror deflecting the laser beam covers almost the entire width of the frosted pane. This has the advantage that the frosted glass does not have to be moved in the X direction.

In a second embodiment variant, the width of the deflector mirror is significantly smaller than that of the frosted pane, so that the entire frosted pane is slidable in both the X and Y directions and can be moved under the fixed diffractive structure, in this embodiment the laser is connected to fixed with frosted glass.

In all embodiments, it can also be provided that the frosted pane is simply absent and the diffraction patterns reflected from the diffractive structure are projected directly onto the recognition surface of the photosensitive sensor devices of the sliding camera under the diffractive structure.

PL 198 952 B1

In the following, the invention is elucidated in terms of its embodiments on the basis of a drawing, in which Fig. 1 shows in a simplified manner a first embodiment according to the invention, Fig. 2 in a simplified manner an embodiment modified with respect to Fig. 1, Fig. 3 - third example 4, a fourth embodiment of the device according to the invention.

In figure 1, an illumination source 1 in the form of a laser is generally arranged in the housing of the document inspection instrument, not explained in more detail, which projects a beam 6 in a horizontal direction. The laser is displaceable in the directions of the arrows 15, 16, this corresponds to the movement of the laser in the direction X.

The ray 6 produced by the laser illumination source 1 is reflected by a profiled, e.g. triangular mirror 3 and is directed in the form of a ray 7 onto the document 26, which may have, for example, a structure as an authenticity feature 4, in the area of ​​which is placed diffractive structure 5.

Of course, the present invention is not limited to placing one diffractive structure 5 within the authenticity feature 4. The diffractive structures 5 may also be isolated on the surface of the document 26 or integrated into the surface of the document 26.

The important thing is that the mirror 3 extends over the entire width of the frosted pane 2 which supports the mirror 3. The frosted pane 2 is slidable in the scanning directions 22 (this corresponds to the Y direction) under the stationary diffractive structure 5.

The laser beam 7 projected onto the diffractive structure 5 is thus reflected in the form of diffracted rays 8, 9, 10 and produces on the frosted glass 2 the diffraction pattern 11-13 characteristic of the diffractive structure 5.

The size, intensity and configuration of the diffraction pattern 11-13 on the frosted glass 2 is a measure of the authenticity of the diffractive structure 5 on document 26.

Figure 2 only shows that (as in Figure 1) a matrix scan camera 18 is placed under the frosted glass 2, the lens of which 17 is in the path of rays 19 on the frosted glass 2, and thus detects all diffraction patterns 11- 13 formed on the frosted glass 2 and recognizes them by means of the CCD 20 chip.

Figure 2 shows an embodiment modified from Figure 1, where it can be seen that the laser light source 1 is connected to the frosted glass 2 by means of a holder 14. The frosted glass 2 is slidable in the directions of the arrows 15, 16, such as also in the directions of the arrows 22.

This embodiment has the advantage that only a relatively small mirror 3 'can be provided, the length of which is significantly less than the width of the frosted glass 2, the frosted glass 2 then having to be made to be slidable in the X direction and the Y direction.

In this embodiment - as described by Fig. 1 - the camera 18 is placed under the frosted pane 2, the diffraction pattern being projected onto the image field 21 of the CCD chip 20.

Figure 3 shows in a simplified manner that it is also possible to omit the frosted pane 2 altogether, with the result that the diffraction pattern 11-12 is projected directly onto the image field 21 of the CCD chip.

Figure 4 shows a schematic view of the structure of the device according to the invention, here the laser light source 1 is mounted on the housing. The rays 6 generated by the laser are incident on the rotating mirror 23, which is pivotable about the rotation axis 25 within a certain range of the angle φ. The laser beam 6 'deflected by the rotary mirror 23 is then deflected by the telecentric mirror 24 fixed to the housing of the telecentric mirror 24 into the laser beam 6 and directed onto the mirror 3 deflecting it, from where it falls on the document 26 or its authenticity feature 4 as laser beam 7. with a diffractive structure 5.