RU2455690C2 - Method and apparatus for identifying raised material - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: surface of a document is illuminated with at least one inclined radiation beam so that any raised material on the surface of the document reflects radiation. A surface with raised material is identified by at least one radiation detector. The image is then processed in order to determine the presence of raised material on the surface of the document. The illumination step causes reflection and/or a shadow formed by at least one edge of the raised material. The processing step identifies the location of the material using said reflection and/or shadow of at least one edge.

EFFECT: high accuracy of identifying areas of raised material.

55 cl, 15 dwg

Description

FIELD OF THE INVENTION

The present invention relates to a method for detecting a section of embossed material on a document surface. An apparatus for implementing the method is also disclosed.

State of the art

Many different applications provide documents that contain a section of embossed material. Typically, this is material that is either intentionally added to the surface of a document, or as a result of a third party. Often, it is desirable to be able to detect whether such material is intentional or random, whether it forms part of a document or is attached to it. One specific application where such a procedure is important is in the field of document security.

An adhesive tape applied to documents such as banknotes corresponds to this type of embossed material. It is desirable to be able to detect the presence of such a tape automatically, as this may indicate a damage to the document and the document (such as a banknote) may then be removed from circulation. The tape may also be present in counterfeit bills, such as “composite bills”. One similar method for detecting tape is provided in US 4,525,630, in which photodetectors measure the level of light reflected specularly and diffusely from a portion of a document, this comparison makes it possible to detect adhesive tape due to the difference in its reflective properties compared to those directly from the banknote.

Despite this, it is necessary to improve the detection of such embossed material, not only regarding the type of material that can be detected, but also because of the increasingly sophisticated deceivers and other persons interested in the reverse side of the document security. Therefore, there is a need to improve the ability to detect embossed material on documents.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, we provide a method for detecting a portion of a relief material on a document surface, comprising illuminating the document surface with at least one oblique emitted beam, so that any relief material on the document surface reflects radiation, forming an image of the surface containing the relief material using at least one radiation detector and image processing to detect the existence of embossed material on the surface of the document and, in this case, the illumination causes reflection and / or shadow produced from at least one edge of the embossed material, and the processing step detects the location of the material using said reflection and / or shadow from at least one edge.

We found that the existence of embossed material can be successfully detected in a very efficient and accurate way using radiation incident on the surface of the document at an angle, combined with detection of the image of the document illuminated in a similar manner and subsequent processing of the image data.

Essentially, the image is processed to detect the existence, in other words, the presence of embossed material. Naturally, it is not only the existence of the material that is detected, but also with appropriate processing, its location is detected.

The types of documents that can be used with the present invention include generally stiff documents, such as boxes or other containers, although, as a rule, the invention finds particular application with relatively thin flexible documents such as sheet materials. Preferably, the surface of the document is substantially flat, at least during the steps of lighting and image acquisition (in the case of thin documents), as this provides a relatively large, simultaneously displayed portion of the document. In many cases, the illumination causes reflection from at least one edge of the material, and therefore the processing step, in such cases, is better suited to detect the location of the material using the identified reflection from at least one edge. Lighting can also, or instead, cause a shadow to appear from at least one edge, in which case the processing step can detect the location of the material by identifying the position of the shadow. A combination of each of these two methods described above is preferred. Thus, the embossed material may include material added to the document after processing the document. The embossed material may include material attached to the surface of the document by a third party other than the document manufacturer or designer.

In general, the invention is most effective when large angles are used between the normal to the plane defining the surface of the document and the light source (therefore, about 90 °) until a good contrast is achieved between the relief material and the surrounding surface of the document. Preferably, such an angle is 70 ° or higher, and more preferably 80 ° or higher.

The method is also preferably performed using a radiation source with a high collimation angle, at least in a direction substantially parallel to the normal to the surface of the document. Collimation in a plane substantially parallel to the same as the surface of the document can also provide improved detection of embossed material.

Although a single localized radiation source could be used, and therefore effectively acting as a localized or even a point source, it is preferable to provide a plurality of emitted rays propagating in one or more directions. They can be provided by a plurality of emitting sources as individual radiation sources, or they can act together as a common diffuse source, usually spreading in one or more directions. The emitted rays can therefore be provided from radiation sources located mainly along lines to one or more sides of the surface of the document.

In addition, the emitted rays can be provided from radiation sources located in a dispersed manner around the surface of the document. However, in all cases it is advisable that the radiation sources are located mainly in a plane parallel to the surface of the document (and almost coplanar in order to provide a large angle). This ensures that any and each of the boundaries of the embossed material on the surface of the document can be used to identify the position of the embossed material.

In order to receive radiation, a number of different types of devices can be used, they have the ability to receive an image either by mechanical scanning, or, preferably, by composing a photodetector having a field of view in order to receive radiation from various parts of the document and the relief material. Depending on the characteristics of the device, one or more sensors (photodetectors) can be used, although usually each is placed so as to receive radiation along a path that defines a small angle relative to the normal to the plane of a specific part of the surface of the document under study. Typically, such a small angle is 10 ° or less relative to the normal to the plane. This angle effectively provides a plan view of the document. It should also be noted that the detector (s) can, in addition, or in addition, be placed to receive reflected radiation (both specularly and diffusely) or transmitted radiation, or, where a number of detectors are provided, combinations of each of them. For the transmitting detector, the detector is placed on the opposite side of the document relative to the embossed material so that the radiation of the detector is transmitted through the document until it is received.

Two radiation detectors can be provided in one device, one of which is located so as to detect light specularly reflected from the surface of the document, and the other to detect light diffusely reflected from the surface of the document, these detectors together produce corresponding images that can be used in specific image processing methods in the practice of the invention. In addition, under certain circumstances, it is advisable to promote the image of the document in the “bright field” mode either later or simultaneously. In this case, the radiation source is ready to provide light rays along or at a small angle to the normal that defines the document plan being checked. The resulting bright field image is then used in subsequent processing.

A number of processing methods suitable for use in the invention include the following main steps:

a) filtering the image with an edge filter;

b) identification of straight lines of candidates within the filtered image;

c) comparing detected identifiable candidates with a model of embossed material to be detected; and

d) positioning of the material based on comparison.

Therefore, edge filtering is used to compare the image with a model that represents the expected physical features expected to be detected in the relief material of interest. A model may include a predefined template or “reference model” containing data representing a clean or genuine document (such as a banknote), including data providing expected features, such as lines, security devices, or other signs that might otherwise be misidentified as unpredictable relief material.

In the case of using mirror and diffusely reflected images, the image processing step may include:

a) identification of candidate sites by comparing mirror and diffuse-reflection images;

b) filtering the mirror and / or diffusely reflected images with an edge filter;

c) identification of straight lines of candidates within the filtered image;

d) comparing the identified candidates with the model of the relief material to be detected; and

e) location and material based on comparison.

Step (c) may include eliminating the presence of candidates within a predetermined pattern.

In the case of using detectors for specular and diffuse reflection, the solid portion of the embossed material is likely to behave differently with respect to intrinsic specular and diffuse reflection compared to the surrounding material. A comparison between such images will be able to locate, including the boundaries of the material being studied.

In any case, taking appropriate lighting conditions, the embossed material can provide a bright reflection from one edge facing in the direction of lighting, and a shadow from the edge facing opposite from the direction of lighting. In this case, the identified candidates can be divided into positive candidates representing increased intensity relative to the background, and negative candidates representing a decrease in intensity relative to the background. Therefore, the model can be adapted to search for pairs of edges, such that indicate, for example, the presence of a strip of tape. The method also preferably further comprises the step of identifying one or more own edges of the document and removing them from the candidates.

Typically, the method further comprises analyzing the candidates to obtain dimensional data, and using dimensional data in the comparison step. The model may therefore include the classification of candidates into pairs of separate parallel lines. Depending on the model, candidates can be identified as one or more straight lines, an irregular (wavy) line, or a curved line. The model may also include a classification of such lines located within a predetermined separation range and / or the presence of a predetermined length range. The model may further include classifying lines by shapes, such as rectangles. The model may also further include consideration of the sharpness of lines within the image.

It will also be appreciated that not all material that can be embossed with respect to the main surface of the document is actually embossed material of the type that is of interest for detection, for example, due to material defects, including manufacturing defects on its own surface wrinkles and other damage. The model is preferably adapted to perform a sufficient number of tests and analyzes in order to distinguish between such defects and the desired goal - embossed material.

The embossed material can take many forms, including tape, security devices (such as a hologram), embossed printing (such as intaglio printing), and other surface decoration. Usually, however, the material represents a type that protrudes above the flat surface of the document and provides a common plateau-shaped portion of the material, embossed with respect to the surface of the document, a plateau defined by peripheral edges (flat and / or curved).

A document that is a valuable document, such as a protected document, similar documents, including banknotes, checks, certificates and identification documents (including passports), is preferred.

The present invention is also not limited to the type of radiation used, although it is generally preferred to use ultraviolet, visible or infrared radiation, or any combination thereof.

In accordance with a second aspect of the present invention, we provide an apparatus for detecting a portion of a relief material on a document surface, comprising at least one light source for illumination with a corresponding oblique emitted beam, a document surface mounted in an inspection position such that any relief material reflects radiation on the surface of the document, causing reflection and / or shadow produced from at least one edge of the embossed material, at least one an radiation detector for acquiring an image of the illuminated surface of the document; and a processor adapted to process the received image from the radiation detector in order to identify the presence of a relief material on the surface of the document, identifying the location of the material using said reflection and / or shadow from said at least one edge.

Therefore, this device is suitable for implementing the method of the first aspect of the invention. Radiation sources can take many forms, including lamps, lasers, LEDs, and so on. Preferred collimation, at least in a direction parallel to the plane of the surface of the document, can be achieved by an aperture or by using a specific device (the presence of innate collimation, for example). A laser may be used to implement the invention, although with regard to other sources, and in particular when using a laser beam, it may be necessary to cause relative movement between the source, the document and the detector in order to scan the surface of the document together with the emitted beam and ensure that embossed material is detected, if any.

Extended or multiple sources can be used to eliminate the need for relative movement, although relative movement can still be further applied. In the case of two sources, for example, one can be placed on one or the other side of the document relative to the inspection plane, although each of them actually lies, for example, above the surface containing the embossed material. Many radiation sources can also be used to define a line along one or more sides of the surface of the document, although they can effectively make up a single common source for each line. In order to ensure collimation along the surface plane of the document being checked, it is preferable, in the case of a dispersed source (either from one or more emitters), that the plurality of provided apertures are located along the line length so as to limit the width of the beam incident on the document surface in the plane parallel to the document surface ) from each source or from each part of the source.

In other cases, it may be desirable to provide an annular arrangement of the radiation sources so that they are located around the normal defining the location in question on the surface of the document. Such sources can be provided equidistant from the normal so as to be located in a ring or circle, although this is not essential. It is preferable to provide a full circle of sources, either as a plurality of sources, or as a general expanded circular source such that the emitted beam hits the document from all angles around the full circle. Typically, a plurality of apertures can be distributed along the length of such a dispersed source or sources so as to limit the beam width in the plane of the document in each case.

It is preferable for all radiation sources, however, so that they are located, to a large extent, in a parallel plane (although not coplanar) with the surface of the document. The radiation sources can also be located or, in addition, so as to cause specular reflection of radiation or diffuse reflection of radiation, respectively. As described previously, it is preferred that the emitter is positioned to provide a beam width of at least 70 ° or more and preferably 80 ° or more to the normal to the plane. This provides a "dark area" of lighting. If an additional “bright area” of illumination is needed, in this case a radiation source can be located to ensure that the rays are emitted forward or at a small angle (about 10 ° or less) to the normal that defines the surface of the document during inspection.

At least one radiation detector is also preferably arranged to receive radiation forming a path defining a small angle (preferably 10 ° or less) relative to the normal to the surface. Composite radiation detectors can be provided, for example, for receiving radiation detected specularly and diffusely. One or more radiation detectors may also be arranged to receive radiation transmitted through a document. They can be used in place of or in addition to reflected radiation detectors. While various radiation sources can be used to produce ultraviolet, visible, or infrared light, radiation detectors are used to obtain images of the document surface when located in the inspection position and therefore such radiation detectors each include a camera, a CCD, a linear scanning device, or other photodetector.

In the case of a sheet processing apparatus, the inspection position usually comprises part of a document transport path, whereby multiple documents periodically become in the inspection position to detect embossed material. Subsequent processing of documents usually depends on the outcome of the discovery process.

It is particularly preferred that the device is used in a banknote processing device comprising at least one input collector, at least one output collector and a transport system adapted to transport banknotes from at least one input collector along the transport path to at least one output collector. The device in accordance with the second aspect of the invention can be located along the transport path to detect the presence of embossed material on the surface of banknotes.

Brief Description of the Drawings

Some examples of the method and devices in accordance with the present invention are described with reference to the accompanying drawings, in which

Figure 1 shows a first example for detecting a tape;

Figure 2 shows a second example for detecting a tape illuminated from two sides;

Figure 3a shows how a smooth, shiny surface reflects radiation;

Fig. 3b shows how rough surfaces cause diffuse reflection;

Figure 4 is a top view from a point of a radiation source;

Figure 5 shows an elongated collimated diffuse source;

6 shows a ring source device;

7 shows an example of the use of an optical waveguide;

Fig. 8 shows processing for edge detection;

Figure 9 shows the differences between tape detection and wrinkles;

10 shows an edge treatment for wrinkles and tape;

11 is an image with side lighting illustrating the visibility of the embossed material;

12 is a view showing deep wrinkles in addition to a matte treated tape;

13 shows an additional image with slight wrinkles and a matte ribbon;

Fig. 14 is a transmitted image.

Description of examples

We are now discussing methods and devices for the optical detection of embossed materials (for example, tapes, foils or even intaglio printing) on documents (for example, banknotes and vouchers). The key components of the proposed method is “dark field lighting” and subsequent image analysis. Illumination of a dark field implies illumination of the side at a rather large angle with respect to the normal to the surface of the document (usually 70 ° or more). This makes the three-dimensional structure of the relief material of the document visible using effects including:

1. Lateral illumination: in case of a single lateral illumination, the edges of the embossed material that oppose the direction of illumination appear bright, the edges opposite to the illumination appear shaded (dark);

2. Scattered side lighting: with scattered lighting, all edges of the relief material in the image will appear bright;

3. Measurement of surface roughness: various surface features (roughness) of the embossed material and the open document can produce different angular propagations of light reflection and, thus, a change in intensity or a change in spatial intensity statistics (textures) in the image under consideration.

The method may use one or more of these three effects in combination.

Model-based analysis involves examining the intensity of the image and the edges, respectively, as well as its options resulting from this, the filtered edges, to distinguish the target material of interest, for example, tape, from other structures such as wrinkles.

The method under consideration will lead to the best results with reflective imaging in most cases, although transmission may be advantageous in some applications. In this case, the lighting is not on the same side of the document as the camera or sensor.

Some examples are now described in more detail.

Example 1: Edge marking with a single side source (pairs of light and dark edges)

Figure 1 shows the first example in terms of the physical principle of operation, since it is associated with optics. A document (in this case, a banknote) is viewed from above by a CCD camera in an attempt to detect adhesive tape fixed to the surface of the document. Alternatively, the camera can be replaced with a linear scanning device (camera or contact image sensor) and the banknote moves perpendicular to the line being read, allowing the line reader to observe various consecutive stripes of the document line by line.

In contrast to the conventional image, which seeks to minimize the effects of shading by perfectly illuminating the document close to a 0 ° angle to the surface normal, the tape detection lighting proposed in the present invention is positioned so that the angle between the light and the document normal is close enough to 90 ° to maximize the shading effect caused by the three-dimensional structure of the document base.

In this configuration, the tape is detected as a rectangular structure with edges that oppose the direction of illumination, seeming bright, and edges that are opposite to lighting, seeming dark (shaded) in the image. Even for one way or another almost invisible (not shiny) tape, this type of lighting is undoubtedly revealing the structure of the tape.

Example 2: Diffuse lighting from two or more sides (light edges)

An alternative figure 1 arrangement is shown in the example in figure 2 with directional lighting on both sides of the analyzed area at the same angle. As a result, the edges of either side of the object will appear bright. This has advantages since light edges are usually easier to detect. However, the difference between opposing and opposite edges in the direction from the lighting disappears.

By adding more sources of directional light at the same angle around the analyzed area, the lighting will ultimately become annular.

Example 3. Shiny reflections that make the tape appear darker

Regardless of the choice of lighting, as described above (one-sided or dispersed), an additional, very important effect is observed with such lighting of a dark field.

Depending on the intrinsic structure of the surface, any material has a specific light distribution of reflection in comparison with the emission angle (see Figs. 3a and 3b). In general, a smooth surface concentrates the reflection at the same angle of incident light to the normal to the plane (“brilliant” reflection), while a rough or complex structured surface can reflect light in almost all directions (diffuse reflection).

Therefore, observing an object at an angle quite different from the incident light, the object appears brighter if its surface is rough, and darker if it has a smooth surface. In the case of a perfect “brilliant” reflection, the object may even appear completely black. This effect can be exploited as an indicator of surface roughness using the ratio of the intensity measured under dark field illumination and the intensity measured under illumination parallel to the normal to the surface (bright field).

Since printed documents usually have a very finely structured (rough) surface, objects attached to them (in particular, tape) will in most cases alter the surface smoothness of the corresponding area, which reduces to a rectangular spot that appears darker than an open surface.

Using the intensity ratio, the effect of surface color can be eliminated. The resulting image of the relationship can be called an “image of surface roughness”.

If the authenticity of the document is known (for example, a separate bill), the bright area of the illuminated image does not actually need to be measured at runtime, but can preferably be stored in the model for combination with the measured dark field image.

With the help of an additional explanation, various layouts of radiation sources are described.

Layout 1. Display the edge of a single side source (a pair of light and dark edges)

4 shows one embodiment of a lighting arrangement using a single point source, as in the case of the first example. Figure 4 can be considered as a view from the camera, with a direction of view, mainly along the normal to the surface of the document. The tape, located, as shown, on the surface of the document, can be determined using such a layout.

Layout 2. Edge display using an elongated source (a pair of light and dark edges)

Alternatively, a matrix of directional sources can be used as a source located perpendicular to the normal to the surface. They can also be used in the implementation of the first example. An arrangement is shown in FIG. 5. To limit the space in which each of the sources produces distributed radiation of the angles of the rays transverse to the plane of the document, a large number of apertures are provided.

The location of the radiation at an angle of 45 ° relative to the orientation of the rectangular document is optimal for detecting horizontal or vertical tapes. However, diagonal ribbons will have edges parallel to the direction of radiation, giving neither shadow nor bright reflection from such edges (as shown in FIG. 5).

In the cases of each of the examples described here, the radiation sources are collimated in a direction parallel to the normal to the plane, in other words, the radiation waves can be thought out for the presence of common components in the direction parallel to the normal to the document plane.

Layout 3. Common lighting (light edges only)

If the intention is to mark all the edges of the embossed material as light, a layout is possible as shown in the ring arrangement in FIG. 6, ensuring that all edges are equally lit. Lighting can be scattered perpendicular to the normal to the surface, but must be directed again or collimated (as a point source) in the direction normal to the surface (as in FIG. 2).

Arrangement 4. Arrangement of diffused lighting creating illumination of the edges

For line cameras and line-sensing contact image sensors, it may be preferable to use two thin light strips (optical fibers or LED arrays) for either of the two sides of the scan line. This is illustrated in FIG. 7. In addition, a point source of a collimated nature in the direction of the surface normal will be important for preserving the features of dark-field illumination.

Now we will return to how the image can be detected.

Discovery and processing

Fig. 8 schematically describes an edge image obtained from the primary readout chamber, illustrated in Fig. 4, after filtering, what is referred to here as edge coloring (see below). It is also suitable for layout relative to example 1.

In addition, the lower part shows a one-dimensional plan, equivalent to one line of the processed image.

The tape detection method according to this example mainly includes the following steps:

1. Image filtering with edge filter.

2. Hog transformation or any other way of finding candidates for straight lines in the image.

3. Edge coloring: sorting the edges into positive (strict localization to increase brightness) and negative (strict localization to decrease brightness) candidates. This can be achieved by considering the second derivative of the image.

4. Selecting a list of candidate edges in the image. This decision will take into account the structure of the edge of the document without tape (if known in advance).

5. Analysis of the edge structure in the image in accordance with the tape model.

The tape model used for detection refers to one or more of the following characteristics:

one). The tape, in almost all cases, appears close to a rectangular structure with at least left and right sides located almost completely parallel (as opposed to the beginning and end of the tape).

2). Pairs of parallel edges of the tape structure should include a positive (bright) and corresponding negative edge (shaded).

3). The edges of the tape should be between the minimum and maximum width.

four). A tape is an approximately rectangular object of a certain minimum length.

5). Each edge of the tape is usually very sharp (corresponds to the peak of a certain maximum width when filtering the image).

Both tapes on the document and wrinkles of the document base create edges in the image (Fig. 9) along with shadow effects of similar intensity.

However, the following features allow wrinkles to be excluded from the list of candidates in the processed image:

i). Wrinkles have a much smaller width, so the positive and negative edges will be very close;

ii). Wrinkles are usually equivalent lines of variable width in the filtered image of the edge; and

iii). Wrinkles have, as a rule, less regular structure than the edges of the tape, i.e. not quite straightforward.

Figure 10 schematically depicts the idea in a similar sense to Figure 8.

The detection in the case of Example 2 works in a similar manner to the aforementioned in Example 1, except that it is not possible to take advantage of edge coloring to pair the edges during the analysis step. All other modeling characteristics are still applicable.

Detection using a Roughness Surface Image can be used in accordance with Example 3. The effect of darkening a smooth (shiny) surface under dark field illumination will draw a dark spot in the image of the roughness surface in the case of a relief object with a similar surface characteristic, for example, a tape, will be clearly indicated as almost rectangular dark strip.

Since the ribbon is likely to be transparent, the main printed sample of the document will still be visible. In this case, it may be preferable to use infrared radiation. 11 shows how a “shiny” tape can be made visible using dark field lighting using an image of a roughness surface.

In a variety of methods, similar to those based on edge comparisons, the corresponding detection algorithm will first identify candidate areas for embossed areas and then compare them with the model (for example, including the requirements for parallel edges, length and width ranges, etc.)

Similarly, measures must be taken to avoid false selection results, such as wrinkles, print defects, stains, etc.

The effectiveness of the above method in FIG. 11 depends on the surface roughness of the tape. In the case of a magic tape that has a rough surface, the location of the tape is more difficult to detect since this tape does not significantly reduce the intensity in the dark field image and can be lost in the presence of other surface effects and printing. However, magic tape can usually be detected due to a change in local statistics (structure) of the intensity of the observed image. In case the statistics do not change, then the magic tape will be detected using the methods based on the comparison of the edges described above. 12 shows an example of an “unfavorable” scenario in dark-field lighting with deep wrinkles. It will be appreciated that the matte coating of the tape in this case means that edge extraction may be required. An additional application example of a matte coated tape with less wrinkling is shown in FIG. 13.

Fig. 14 shows that a "transmitting" arrangement may be used, a figure showing, in particular, edge effects (upper part of the center of the image).

Claims (54)

1. A method for detecting a section of embossed material on the surface of a document to be protected, comprising:
illuminating the surface of the document to be protected with at least one inclined radiation beam in such a way that any relief material on the surface of the document to be protected reflects radiation;
obtaining an image of the surface containing the embossed material using at least one radiation detector; and
image processing to detect the presence on the surface of the protected document of embossed material;
wherein the illumination causes reflection and / or shadow formed by at least one edge of the embossed material, and at the same time, at the processing step, the location of the material is detected using the aforementioned reflection and / or shadow from at least one edge. 2. The method according to claim 1, in which the surface of the protected document is essentially flat, at least during the stages of lighting and image acquisition. 3. The method according to claim 1, wherein the embossed material includes material added to the security document after the production of the security document. 4. The method according to claim 1, in which the embossed material includes a material attached to the surface of the protected document by another participant in the process, except for the manufacturer of the protected document. 5. The method according to claim 1, in which the surface is determined by the normal to the plane and in which each emitted beam is directed at a large angle with respect to the normal to the plane. 6. The method according to claim 5, in which the angle of each beam normal to the plane is 80 ° or more. 7. The method according to claim 1, in which each emitted beam is essentially collimated in a direction substantially parallel to the normal to the surface of the document to be protected. 8. The method according to claim 7, which further comprises a plurality of emitted rays. 9. The method of claim 8, in which emitted rays are provided from radiation sources located essentially along lines to one or more sides of the surface of the document to be protected. 10. The method according to claim 8, in which the emitted rays are provided from radiation sources located dispersed around the surface of the protected document. 11. The method according to claim 9, in which the radiation sources are located essentially in a plane parallel to the surface of the protected document. 12. The method according to claim 1, in which the surface of the protected document is determined by the normal to the plane and in which each radiation detector is located so as to receive radiation following the path that defines a small angle with respect to the normal to the plane. 13. The method according to item 12, in which a small angle is 10 ° or less. 14. The method according to claim 1, in which at least one radiation detector is located on the back side of the protected document relative to the material, so that the detected radiation is passed through the protected document until it is received. 15. The method according to claim 1, in which the radiation detector is provided and located so as to detect light specularly reflected from the surface of the protected document and in which the image processing step comprises searching for a rectangle with parallel lines within the image. 16. The method according to claim 1, in which two radiation detectors are provided, one of which is arranged to detect light specularly reflected from the radiation surface, and the other is arranged to detect light diffusely reflected from the surface of the document to be protected. 17. The method according to clause 15, further includes acquiring an image using specular reflection and an image using diffuse reflection. 18. The method according to claim 1, further includes a stage on which the protected document is simultaneously and / or sequentially illuminated by a beam emitted along or at a slight angle normal to the plane of the protected document, so as to obtain a bright image field of the protected document. 19. The method of claim 18, wherein the bright image field is used in the processing step. 20. The method according to claim 1, in which the step of image processing further includes:
image filtering by the edge filter;
identification of straight candidate lines within the filtered image;
comparing identified candidates with a model of embossed material to be detected; and
positioning of the material based on the specified comparison. 21. The method according to claim 20, in which the model includes data representative of a clean or genuine protected document. 22. The method according to claim 20, in which the image processing step further comprises:
identification of candidate sites by comparing mirror and diffuse reflections of images;
filtering mirror and / or diffuse reflections of images or their relationships or differences, with an edge filter;
identification of straight candidate lines within the filtered image;
comparing the identified candidates with a model of embossed material intended for detection; and
locating material based on comparison. 23. The method according to item 22, wherein the step of identifying straight candidate lines within the filtered image comprises eliminating the presence of candidates within a predetermined pattern. 24. The method according to claim 20, which further includes, after the identification step, the separation of the identified candidates into positive candidates, representatives of increased intensity in relation to the background, and negative candidates, representatives of reduced intensity in relation to the background. 25. The method according to paragraph 24 further includes the step of identifying one or more edges of the document to be protected and deriving them from the candidates. 26. The method according to claim 20 further includes analyzing the candidate straight lines to obtain dimensional data and using dimensional data in the comparison step. 27. The method according to p, in which the model includes a layout of straight lines of candidates in pairs of spaced parallel lines. 28. The method according to p, in which the model includes an arrangement of lines spaced within a predetermined range of diversity. 29. The method of claim 26, wherein the model includes an arrangement of lines lying within a predetermined length range. 30. The method according to p, in which the model includes a layout of lines to form a rectangle. 31. The method according to claim 20, in which the model includes a predetermined sharpness of the lines. 32. The method according to claim 1, in which the model is additionally configured to distinguish defects between the surface of the protected document and the relief material. 33. The method according to claim 1, in which the method is adapted to detect embossed material in the form of one or more tapes, a protective device, embossed printing attached to the protected document. 34. The method according to claim 1, in which the embossed material protrudes above the flat surface of the document to be protected and provides a common plateau-shaped portion of the raised material, embossed with respect to the surface of the document to be protected and defined by one or more peripheral edges. 35. The method according to claim 1, in which the radiation is ultraviolet, visible or infrared light. 36. A device for detecting a section of embossed material on the surface of a protected document, comprising:
at least one radiation source for illumination, with a corresponding oblique radiation beam, of the surface of the document to be protected installed in the inspection position so that any relief material on the surface of the document to be protected reflects the radiation, causing reflection and / or shadow formed by at least from one edge of the embossed material;
at least one radiation detector for acquiring an image of the illuminated surface of the document to be protected; and,
a processor configured to process an image received from the radiation detector so as to identify the presence on the surface of the document to be protected of embossed material by identifying the location of the material using said reflection and / or shadow from said at least one edge. 37. The device according to clause 36, in which each radiation source is configured to generate a beam essentially collimated in a direction substantially parallel to the normal to the surface of the document to be protected. 38. The device according to clause 36, in which the radiation source is located on opposite sides of the protected document. 39. The device according to clause 36, in which many radiation sources are located essentially along the lines to one or more sides of the surface of the protected document. 40. The device according to clause 37, in which a number of radiation sources together are part of a common extended source having many apertures dispersed along its length. 41. The device according to clause 37, in which there are many radiation sources covering the protected document. 42. The device according to paragraph 41, in which the sources are part of a common covering source having many apertures dispersed along its length. 43. The device according to clause 36, in which the radiation sources are located essentially in the plane parallel to the surface of the protected document. 44. The device according to clause 36, in which the surface of the protected document is determined by the normal to the plane and, in which at least one radiation source is configured to create an emitted beam that defines a large angle relative to the normal to the plane. 45. The device according to item 44, in which the radiation source is made so that the angle of the beam with a normal to the plane is 80 ° or more. 46. The device according to clause 36, in which the surface of the document to be protected is determined by the normal to the plane and in which at least one radiation detector is located to receive radiation following the path that defines a small angle relative to the normal to the plane. 47. The device according to item 46, in which a small angle is 10 ° or less. 48. The device according to clause 36, in which the radiation detector is located to receive specularly reflected radiation, and where the second radiation detector is located to receive diffuse-reflected radiation. 49. The device according to clause 36, in which at least one detector is located on the back side of the protected document relative to the material so that the detected radiation is passed through the protected document until received. 50. The device according to clause 36 further comprises a radiation source for placement in such a way as to create a bright image field, illuminating the protected document with an emitted beam along or at a small angle to the normal to the surface of the protected document. 51. The device according to clause 36, in which each radiation source is an ultraviolet, visible or infrared radiation source. 52. The device according to clause 36, in which the radiation detector is selected from the group: camera, CCD or linear scanning device. 53. The device according to clause 36, in which the inspection position includes part of the path of transportation of the protected document. 54. A banknote processing device comprising at least one input collector; at least one output collector, a transport system configured to transport banknotes from the input collector or collections along the transport path to the output collector or collections; and the device according to clause 37, located along the transport path for detecting embossed material on the surface of banknotes.

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