Radiant energy – Luminophor irradiation
Reexamination Certificate
2001-07-03
2004-08-31
Hannaher, Constantine (Department: 2878)
Radiant energy
Luminophor irradiation
Reexamination Certificate
active
06784441
ABSTRACT:
The invention relates to a handheld 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. Such a sensor has been disclosed by the subject matter of DE 41 17 011 A1, in which low-intensity radiation, in particular diffuse 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 cannot, 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.
Furthermore, with the known sensor it is impossible to provide manual operation, in which a manually controlled sensor is moved over an object which has one or more signets on it and whose authenticity is intended to be checked. Manually controlled operation with this sensor is not described.
The invention is therefore based on the object of developing a handheld sensor for authenticity identification of signets on documents such that luminescent signets (that is to say signets with identification features based on fluorescence, phosphorescence, up-conversion, etc.) on the document can be identified over a considerably larger area on the document, and manually controlled operation is possible.
In order to achieve said object, the invention is distinguished by the technical teaching in claim
1
.
A handheld sensor according to the invention is preferably used when it is also retrospectively intended to check the authenticity of authenticity signets which are not identified automatically.
However, such a handheld sensor can also be used independently of automatic facilities, for example for authenticity identification of entry cards, credit cards and all other situations which involve fast, highly sensitive checking of identification features, independently of machines.
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 optically excites the identification feature which is arranged on the document, and the optical response 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, can be applied directly to the document itself, but which is also 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 line, 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 handheld sensor is moved over the document 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 use a sensor which is moved by hand to move the measurement window associated with the sensor over a large area of a document, and thus to investigate for the presence of identification features and, in the process, to use the scanning line which is projected onto the document surface to scan a relatively large area 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 reflected wavelength emitted by the identification feature. Expressed in the frequency domain, this means that the excitation frequency is lower than the response frequency.
The invention also relates to other excitation mechanisms, however, such as the use of the “normal” fluorescence effect, in which a specific wavelength is used for excitation and the fluorescent identification 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 area of protection of the invention extends to the use of all said effects, also when combined with one another.
One particular problem in the prior art is solved by particularly simple means by the present invention:
Manually controlled sensors are subject to two mutually contradictory requirements:
According to the first requirement, the evaluation of the signal from the handheld sensor should be as sensitive as possible in order to allow even relatively weak signals to be identified. To this end, it is desirable for the laser which is arranged in the handheld sensor to produce a high-energy laser beam which is as powerful as possible.
However, the contradictory requirement to this is that the laser beam must not lead to injuries if operated incorrectly. For this reason, the laser should be in as low a laser class as possible, in order to avoid the possibility of a high-energy laser leading to injuries to the human body during operation.
These two requirements are mutually contradictory since, firstly, clearly distinguished identification demands a high-energy laser and, secondly, a high-energy laser is undesirable for safety at work reasons.
As a consequence of this, the invention makes it possible to use a relatively high-energy laser to achieve high-sensitivity scanning of a weakly radiating signet, because it is possible to use a relatively high-energy laser source in a laser class higher than class
3
A, while the invention ensures that the laser is switched on only when the handheld sensor has been moved sufficiently close to the scanning surface to be investigated and/or that beam forming measures allow the sensor to be classified in laser class
3
A or lower despite the powerful radiation source. For the former, the invention proposes a sensor system which identifies and evaluates the proximity of the laser to the document surface and, on this basis, controls the switching-on and, if necessary, also the switching-off of the
Ahlers Benedikt
Bailleu Anett
Franz-Burgholz Arnim
Gutmann Roland
Halter Peter
Bundesdruckerei GmbH
Hannaher Constantine
Katten Muchin Zavis & Rosenman
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