Optics: measuring and testing – Document pattern analysis or verification
Reexamination Certificate
2001-06-04
2004-05-25
Glick, Edward J. (Department: 2882)
Optics: measuring and testing
Document pattern analysis or verification
C250S271000, C250S458100
Reexamination Certificate
active
06741336
ABSTRACT:
The invention relates to a sensor for authenticity identification of signets on documents as claimed in the preamble of patent claim
1
, and to a signet which interacts with the sensor and has at least one identification feature. Various embodiments of such a sensor have been disclosed. The subject matter of DE 41 17 011 A1 describes an optical sensor in which, in particular, diffuse, low-intensity radiation is intended to be detected, such as that which also occurs when checking currency bills which are provided with luminescent features.
The sensor system described there comprises a conically widening optical fiber rod and further-processing optics, in which case the radiation coming from the measurement object can be detected over a wide spatial angle using the narrow cross-section end of the fiber rod. Owing to the cross-section conversion, the radiation emerges from the fiber rod at a considerably narrower angle, which is matched to the aperture angle of the subsequent optics.
Although it is possible to detect relatively low-intensity luminescent features using this sensor, the strength of the detected luminescent features must not, however, fall below a specific threshold when they are distributed over a relatively large area. It is therefore still relatively insensitive. This is because the use of a conically formed fiber rod results in the disadvantage that detection can take place only in a region in the form of a point on the document, which fails to occur when the element to be investigated (also referred to as the identification feature) is arranged at other points on the document.
Furthermore, excitation using conventional light sources with visible light (for example incandescent lamps) leads to a relatively weak luminescence signal, which must be detected by the fiber rod and must be supplied to the evaluation optics.
The invention is therefore based on the object of developing a sensor for authenticity identification of signets on documents, such that luminescent signets on the document can be identified over a considerably larger area of the document.
In order to achieve said object, the invention is distinguished by the technical teaching of claim
1
.
The major feature of the invention is that a focused beam which is emitted by a beam source is converted by focusing optics in such a manner that a scanning line, which is roughly in the form of a line, is produced on the surface of the document to be investigated and causes the identification feature, which is arranged on the document, to fluoresce, and the fluorescence signal is evaluated via detection optics by an evaluation unit.
In order to delineate the individual terms from one another, the term “identification feature” is used generally as a feature which verifies the authenticity of a document, which can be applied directly to the document itself, but which can also be arranged in the region of a signet.
The term “signet” describes a mark or a label, a seal, a delineated area of any type or a printed region on a document which is connected (for example by being bonded on) detachably or non-detachably to the document, on which the identification feature is arranged. The later description does not define whether the identification feature is located directly on the document itself or is part of a signet applied to the document and which is connected detachably or non-detachably to the document.
The given technical teaching results in the major advantage that the production of a scanning line, which is approximately in the form of a bar, on the document to be investigated for the first time makes it possible to investigate not only areas in the form of points on the document, but an entire area in the form of a line, which is converted into a corresponding investigation area when the document is moved past the measurement window at a specific speed approximately at right angles to the longitudinal axis of the scanning line.
It is thus now for the first time possible to investigate a document which is moving past the measurement window over a large area for the presence of authenticity features, while the document is being moved past the measurement window of the sensor and, in the process, the scanning line, which is projected on the document surface, scans a relatively large area of the document. The authenticity feature or signet to be investigated can thus be arranged such that it is distributed over a large area of the document. The scanning beam is chosen to be sufficiently long that the signet is reliably arranged in the region of the scanning beam of the document.
It is preferable for the so-called up-conversion effect to be used. In this case, the excitation wavelength is longer than the wavelength emitted from the authenticity feature. Expressed in the frequency domain, this means that the excitation frequency is lower than the response frequency.
However, the invention also relates to other excitation mechanisms, such as the use of the “normal” fluorescence effect, in which the excitation takes place at a specific wavelength and the fluorescent authenticity feature responds at a longer wavelength, which represents the opposite effect to said up-conversion effect.
A third embodiment relates to the fluorescence effect in which the excitation is at the same wavelength as the emission wavelength, but with the response pulse following the excitation pulse with a defined time delay.
All said effects are the subject matter of the present invention, and the protection area of the invention extends to the use of all said effects, also when combined with one another.
The further features of the invention are evident from the following summary, based on key words:
Features of the Sensor System
1. The sensor according to the invention is suitable for mounting in a (high-speed) transport apparatus, and may also be in the form of a scanner.
2. It is suitable for detection of a security feature, predominantly on flat objects.
3. A signet, comprising a color with added up-conversion pigments, is proposed by preference as the detectable security feature. If need be, these pigments can also be added directly in an applied solution, an applied paint, the adhesive or the paper.
4. The sensor is advantageously suitable for detection of a (for example printed-on) security feature with small dimensions (for example 5×5 mm). If the security feature is applied by printing, the printing can be applied within relatively wide limits. The required sensor measurement range must therefore cover the entire possible printed area, although the signet printed on it may appear anywhere in this printing area, and the signet may be several times smaller than the printing area.
5. The measurement area (scanning area, transversely with respect to the transport direction) may, for example, have a size of up to 70 mm, and the small security feature is detected anywhere within this large measurement area.
6. Position-resolved detection is preferably carried out in the transport direction, but position resolution in the direction transversely with respect to the transport direction is only optional.
7. The speed in the transport direction varies from zero to 4 m/s.
8. An embodiment in the form of a two-band sensor is also preferred, in which the test object is illuminated once, and in which two different spectral bands are evaluated. In this case, the received beams are split by means of a beam splitter, are each optically filtered separately, with different pass band wavelengths, and are evaluated in separate receivers. A dichroic mirror is particularly suitable for use as a beam splitter. Alternatively, a spectral measurement could be carried out, in which the presence of one, two or more spectral components and their spectral appearance as well as their intensity would be monitored.
9. An integrated UV luminescence sensor can be used as an embodiment, in which the test object is illuminated with UV light (for example with UV LED at a wavelength of 370 nm or using a discharge lamp), and the luminescence signal is detected in a d
Ahlers Benedikt
Bailleu Anett
Franz-Burgholz Arnim
Gutmann Roland
Halter Peter
Artman Thomas R
Bundesruckerai GmbH
Glick Edward J.
Katten Muchin Zavis & Rosenman
LandOfFree
Sensor for authenticity identification of signets on documents does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Sensor for authenticity identification of signets on documents, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sensor for authenticity identification of signets on documents will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3189119