U.S. patent application number 09/899742 was filed with the patent office on 2003-02-13 for handsensor for authenticity identification of signets on documents.
This patent application is currently assigned to Bunderdruckerei GmbH of Oranienstrasse 91, D-10958. Invention is credited to Ahlers, Benedikt, Bailleu, Anett, Franz-Burgholz, Arnim, Gutmann, Roland, Halter, Peter, Paeschke, Manfred, Weber, Uwe, Zerbel, Hans.
Application Number | 20030030012 09/899742 |
Document ID | / |
Family ID | 7647037 |
Filed Date | 2003-02-13 |
United States Patent
Application |
20030030012 |
Kind Code |
A1 |
Ahlers, Benedikt ; et
al. |
February 13, 2003 |
Handsensor for authenticity identification of signets on
documents
Abstract
A manually controlled sensor for authenticity identification of
luminescent identification features on documents is described, in
which the identification feature is illuminated with an excitation
wavelength and may respond at a different wavelength, with the
response wavelength being detected and evaluated by a radiation
receiver. In order to improve the sensitivity and to comply with
the safety at work regulations, a focused beam (31, 32), which is
emitted from a beam source (1), is converted by focusing optics (2,
3) in such a manner that a scanning bar (22), which is
approximately in the form of a line, is projected on the surface of
the object (5) to be investigated, which causes the identification
region (21) which is arranged on the object (5) to fluoresce in a
luminescent manner in at least one subregion, and the luminescence
signal produced in this way is passed via detection optics (9, 9',
10) to an evaluation unit (11), which evaluates the luminescence
signal. The sensor is intended to be classified in laser class
3A.
Inventors: |
Ahlers, Benedikt; (Berlin,
DE) ; Gutmann, Roland; (Falkensee, DE) ;
Franz-Burgholz, Arnim; (Berlin, DE) ; Bailleu,
Anett; (Berlin, DE) ; Paeschke, Manfred;
(Basdorf, DE) ; Halter, Peter; (Frauenfeld,
CH) ; Zerbel, Hans; (Berlin, DE) ; Weber,
Uwe; (Hamburg, DE) |
Correspondence
Address: |
Rosenman & Colin LLP
575 Madison Avenue
New York
NY
10022-2585
US
|
Assignee: |
Bunderdruckerei GmbH of
Oranienstrasse 91, D-10958
Berlin
DE
|
Family ID: |
7647037 |
Appl. No.: |
09/899742 |
Filed: |
July 4, 2001 |
Current U.S.
Class: |
250/458.1 |
Current CPC
Class: |
G07D 7/128 20130101;
G07D 7/121 20130101 |
Class at
Publication: |
250/458.1 |
International
Class: |
G01N 021/64 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 7, 2000 |
DE |
100 31388.4 |
Claims
1. A sensor for authenticity identification of luminescent
identification features on documents, in which the identification
feature is illuminated with an excitation wavelength and may
respond at a different wavelength, with the response wavelength
being detected and evaluated by a radiation receiver, wherein a
focused beam (31, 32), which is emitted from a beam source (1), is
converted by focusing optics (2, 3) in such a manner that a
scanning bar, which is approximately in the form of a line, is
projected on the surface of the object (5) to be investigated and
optically excites at least a subregion of the identification
feature (21) which is arranged on the object (5), and the optical
response signal from the identification feature is passed via
detection optics (9, 9', 10) to an evaluation unit (11) which
evaluates this optical response signal, and wherein the sensor is
manually controlled.
2. The sensor as claimed in claim 1, wherein the sensor has
proximity identification, which switches on a laser (laser diode 1)
only when the object (5) to be investigated is located closely in
front of and touching an outlet window (7) in the head surface (26,
27) of the sensor.
3. The sensor as claimed in claim 2, wherein the proximity
identification operates without making contact.
4. The sensor as claimed in claim 2, wherein the proximity
identification reacts to diffuse reflection on the surface of the
object (5).
5. The sensor as claimed in claim 2, wherein the proximity
identification operates by touching the object (5).
6. The sensor as claimed in one of claims 2 to 4, wherein, in
addition to the proximity identification, a manually operated
pushbutton (15) is provided, which is coupled in an AND circuit to
the proximity identification or whose previous operation is a prior
condition for activation of the laser after identification of the
proximity within a short time window.
7. A sensor for authenticity identification of luminescent
identification features on documents, in which the identification
feature (21) is illuminated with an excitation wavelength and may
respond at a shorter, longer or equal wavelength, with the response
wavelength being detected and evaluated by a radiation receiver,
wherein the focused beam (32, 33) which is produced on the object
(5) is produced by at least one laser source (1) which passes
through line optics (2, 3).
8. The sensor as claimed in one of claims 1 to 6, wherein the laser
focused beam (32, 33) which is produced by the laser is imaged
differently in the X-direction and Y-direction on the object
(5).
9. The sensor as claimed in claim 7, wherein the focusing in the
X-plane and Y-plane is produced at a different height above the
object (5).
10. The sensor as claimed in one of claims 7 to 9, wherein the
largest angles of the focused beams in the X-plane or Y-plane reach
an angle of more than +/-10.degree. to the optical axis.
11. The sensor as claimed in one of claims 1 to 10, wherein
external light identification is integrated in the reception path
of the authenticity identification of the identification feature
(21).
12. The sensor as claimed in one of claims 1 to 10, wherein the
external light identification is integrated in the arrangement for
proximity identification without making contact.
13. The sensor as claimed in one of claims 1 to 12, wherein the
handheld sensor can be classified in laser class 3A.
14. The sensor as claimed in one of claims 1 to 13, wherein the
laser is pulsed.
15. The sensor as claimed in one of claims 1 to 14, wherein the
sensor has wide-aperture receiving optics with an aperture ratio of
virtually 1 or less.
16. An identification feature for detection using the sensor as
claimed in one of claims 1 to 15, wherein, in order to identify the
identification feature (21) on a document, the signet is equipped
at least in subregions with a pigment which can be detected using
the up-conversion effect.
17. The identification feature for identification using the sensor
as claimed in one of claims 1 to 16, wherein the identification
feature (21) which is in the form of a fluorescent identification
feature, can be detected using the down-conversion effect.
18. The identification feature for detection using the sensor as
claimed in one of claims 1 to 17, wherein in the form of a
fluorescent identification feature, is excited at a specific
wavelength, and responds at the same wavelength.
19. The identification feature for detection using the sensor as
claimed in one of claims 1 to 18, wherein the emission wavelength
of the identification feature has the same wavelength as the
excitation wave, and wherein the pulse response is delayed in time
with respect to the excitation pulse.
20. The identification feature for detection using the sensor as
claimed in one of claims 1 to 19, wherein the pigments are added
directly to an applied solution, to an applied paint, to the
adhesive or to the paper.
Description
[0001] 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.
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] In order to achieve said object, the invention is
distinguished by the technical teaching in claim 1.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] One particular problem in the prior art is solved by
particularly simple means by the present invention:
[0020] Manually controlled sensors are subject to two mutually
contradictory requirements:
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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 3A, 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 3A 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 laser.
[0025] Laser class 3A is a preferred laser class, which on the one
hand allows effective identification even of weakly radiating
signets, while on the other hand precluding health hazards.
[0026] According to a first feature, an important aspect of the
invention is that the laser which is arranged in the handheld
sensor is operated only when the proximity of the head surface to
an object, or even the head surface being placed on an object, with
the signet (identification feature) arranged on said object, has
been identified reliably. This results in eye protection even with
relatively powerful lasers.
[0027] Such proximity identification can be achieved in various
ways.
[0028] A first, preferred refinement provides for the proximity to
be detected by scanning the surface of the object. Such scanning
can be carried out by means of optics and a transmitting/receiving
arrangement, which preferably operates in the IR band, with, for
example, an LED being connected as the transmitting diode, and a
single photo diode or a double photo diode being connected as the
receiving diode.
[0029] When the scanning beam of this arrangement is now reflected
from the object to be investigated, the reflected beam is then
evaluated by the receiving photo diode in the handheld sensor, thus
reliably confirming proximity to the object. The laser operates
only when this proximity has been confirmed, and then scans the
object with the laser beam in order to check the identification
feature.
[0030] In the case of a single photo diode as the receiving diode,
focused optics are used which ensure that only light from the light
spot 24 strikes the photo diode when the object is located directly
in front of or very close underneath the outlet window 7. In the
case of a double photo diode as the receiving diode, a
triangulation evaluation can be achieved. If the object is well in
front of the outlet window 7, then the light imaged by the light
spot 24 strikes one photo diode (the first part of the double photo
diode) which is referred to as the background diode. If, on the
other hand, the object is directly in front of the outlet window,
then the light strikes the other photo diode (second part of the
double photo diode), which is referred to as the foreground diode.
This allows proximity to be identified even more reliably than when
using only one photo diode.
[0031] Another refinement of this technical teaching provides for
touching scanning to be carried out rather than scanning without
making contact. Touching scanning may be, for example, a contact
switch or a pressure sensor which emits a signal only when the head
surface of the handheld sensor has been placed on the object.
[0032] All said proximity identification processes can preferably
be combined with a manually controllable button (switch or
pushbutton), so that the laser is switched on only when this button
is also operated and on identification that the handheld sensor is
in the proximity of the object.
[0033] The given technical teaching thus results in the advantage
that a highly sensitive handheld sensor can also be used for
identification of weakly luminescent signets, and ensures reliable
manual operation while complying with the safety at work
regulations.
[0034] Independently of the identification of the proximity of the
handheld sensor to an object using an identification feature
arranged on that object, as mentioned above, further technical
teaching claims that so-called line optics are used for producing
the laser beams in the handheld sensor. This means that the focused
laser beam produced by the laser is imaged differently in the X and
Y directions on the object. It is preferable for the focusing in
the Y direction to be above the scanning bar produced on the
surface of the document and above the document, that is to say in
the region of the beam path of the sensor (still within the sensor
housing), while the focusing in the X direction is directly on the
object (=document surface) itself. It is furthermore preferable for
the beam angles of the outermost focused beams with respect to the
optical axis to be as large as possible.
[0035] These focusing planes, which are offset with respect to one
another at different heights above the document surface, ensure
that, if the focused laser beam enters an animal or human eye, it
is no longer possible for the beam to be imaged in the form of a
point on the retina of the eye. This avoids point damage to the
retina, since the laser beam is focused at different distances in
front of the retina in the X and Y directions. On the other hand,
illumination of the retina with the image of the elongated scanning
bar takes place with an illumination intensity which is greatly
reduced in comparison to the point image, firstly because of the
offset focusing planes, and secondly because of the steep beam
angles since the 7 mm aperture size of the eye can no longer
receive all the radiation.
[0036] This prevents any adverse effects, forming a health hazard,
to the retina of the eye, even if a somewhat more powerful laser is
used. Thanks to the above-mentioned measures, the sensor can be
classified in a lower, and thus more safe, laser class than without
these measures. For example, on the basis of these measures, the
sensor can be classified in laser class 3A instead of 3B, which
makes a very major difference. Furthermore, thanks to the use of
these special line optics, a somewhat more powerful laser can be
used, which is better for evaluation of weak signals but
nevertheless guarantees that the handheld sensor can be handled
safely.
[0037] In the simplest case, the line optics comprise a cylindrical
lens. However, instead of such a simple cylindrical lens, it is
also possible to use a compound lens, such as a convergent lens, in
conjunction with a cylindrical lens or specially shaped cylindrical
lenses.
[0038] The convergent lens in this case provides the focusing on
the object surface, while the cylindrical lenses produce the highly
divergent (defocused) beams on the object, which form the elongated
scanning bar on the object.
[0039] In order to allow beam angles which are sufficiently large
to attain the advantage for the invention, it is generally
necessary to use two cylindrical lenses in series, and/or to equip
these lenses with a special shape. The cylindrical lenses then no
longer have a circular-cylindrical surface, but an aspherical,
conical surface which is different than it. This allows good beam
guidance to be achieved even at steep beam angles. The shape of the
surface is optimized using optical design software. Alternatively
detractive optical elements can also be used, or Fresnel lenses, or
sinusoidal surfaces. All these elements are part of the line optics
and have characteristics which are similar to those of normal
cylindrical lenses, but are improved for the application.
[0040] The essential features of the invention are repeated, once
again, in abbreviated form below:
[0041] Wide-aperture receiving optics with an f-number of
approximately 1.
[0042] Laser line optics with steep outlet angles in order to
reduce eye and skin danger when using a powerful laser diode, which
at the same time allows classification in a lower laser class. The
aim is laser class 3A or lower, so that there is no longer any
hazard in normal use.
[0043] Additional safety measures:
[0044] Pushbutton: laser transmits its light only when there is
finger pressure on the pushbutton.
[0045] optical light probe or additional, mechanical contact probe
in order to identify this object.
[0046] Time limit: the laser light is only ever emitted for about 2
seconds when the two above criteria are satisfied.
[0047] Identification of small spectral light components from
weakly back-scattering identification features on objects.
[0048] Shadowing of external light by the characteristics of the
handheld sensor; the handheld sensor must be moved into contact
above those points on the object where the identification feature
is applied.
[0049] The handheld sensor scans an area with a width of
approximately 2 mm during movement, thanks to its approximately 2
mm-wide laser line.
[0050] The subject matter of the present invention results not only
from the subject matter of the individual patent claims, but also
from the combination of the individual patent claims with one
another.
[0051] All the statements and features disclosed in the documents,
including the abstract, in particular the physical embodiment
illustrated in the drawings, are claimed as being substantial items
relating to the invention, to the extent that they are novel
individually or in combination when compared to the prior art.
[0052] The invention will be explained in more detail in the
following text with reference to drawings, which illustrate only
one possible embodiment. In this case, further features and
advantages which are substantial with regard to the invention are
evident from the drawings and from their description.
[0053] In the drawings:
[0054] FIG. 1 shows a schematically drawn section through one
embodiment of a handheld sensor according to the invention
[0055] FIG. 2 shows a plan view of an object with an identification
feature arranged on it, and with the scanning bar
[0056] FIG. 3 shows a front view of the handheld sensor in the
direction of the arrow III in FIG. 1
[0057] FIG. 4 shows an illustration of the elements of the handheld
sensor, illustrated in perspective rather than as in FIG. 1
[0058] FIG. 5 illustrates the focused beam in the X- and
Y-directions of line optics
[0059] The handheld sensor has a housing whose cross section is
substantially approximately circular-cylindrical but which may also
be polygonal, oval or square. This housing is annotated 19 in FIG.
1.
[0060] One or more batteries or rechargeable batteries 20 can be
arranged in the housing, and are used to supply power to the laser
diode 1. An external power connection can also be provided on the
housing, instead of the battery 20. A separate battery pack can
likewise be provided, and is connected to the handheld sensor via a
relatively long cable.
[0061] The laser diode 1 produces a focused beam 34, which first of
all passes through one or more focusing lenses 2. These focusing
lenses 2 focus the beam in the X-direction (focused beam 32 in FIG.
5) essentially onto the object plane of the object 5 to which the
identification feature 21 is applied.
[0062] The important feature is that the focusing lens 2 is
followed by line optics 3 which, in the simplest case, comprise a
cylindrical lens. The term "line optics 3" generally means any
optics which are able to produce a scanning bar 22 approximately in
the form of a line or an ellipse. This scanning bar 22 is
illustrated, by way of example, in FIG. 5, and will be described in
more detail in conjunction with this figure there.
[0063] The focused beams 31, 32, which are produced and are
illustrated in FIG. 5 are combined as transmitted beams 28 in FIG.
1, and are passed to a deflection mirror 4, which has been omitted
from FIG. 5, for the sake of simplicity.
[0064] This results in the somewhat elongated scanning bar 22 shown
in FIG. 5, which emerges from the outlet window 7 on the head
surface 26, 27 of the handheld sensor.
[0065] FIG. 3 shows that the head surface area 26 (width of the
scanning head) is considerably larger than, by comparison, the
width of the outlet window 7. This reliably suppresses external
light influences arriving from the side.
[0066] The same generally also applies to the extent of the head
surface 27 in the longitudinal direction (direction of the arrow
23).
[0067] Thus, overall, the focused beam directed at the object 5 is
annotated 6 (transmitted beams).
[0068] Further explanations will be given later, with reference to
FIG. 5.
[0069] The scanning bar 22 produced as shown in FIG. 2 is passed in
the direction of the arrow 23 in the direction of the
identification feature 21 via the object 5.
[0070] Apart from this, in this context, it should be mentioned
that FIG. 2 illustrates, only schematically, a light spot 24 of the
proximity sensor system which scans the document surface. The
evaluation of the reflected component confirms the presence of the
document. The light spot 24 covers the scanning bar 22 only by way
of illustration. It can also be arranged alongside, behind or in
front of the scanning bar.
[0071] The term light spot 24 is, in general, not intended to imply
that this is visible light. It may also be in an invisible band,
specifically in the IR or UV bands.
[0072] The beam component reflected from the identification feature
21, which may be at a different wavelength than the transmitted
beam 6, is radiated back as a received beam 8 into the handheld
sensor, and is focused via a first receiving lens 9.
[0073] A second receiving lens 9', which produces further focusing,
can be arranged behind the first receiving lens 9.
[0074] The received focused beam, which has been received and
focused in this way, is, finally, passed via an optical filter 10
to illuminate a receiving element 11 which may, for example, be a
photo diode or an avalanche photo diode.
[0075] A photo multiplier may also be used instead of the receiving
element 11 described here.
[0076] The described laser optics result in the advantage that the
use of specific line optics results in the production of a
transmitted focused beam with steep beam angles, and this in turn
allows the handheld sensor to be classified in a comparatively low,
safe laser class.
[0077] A first embodiment of identification of the proximity of the
handheld sensor to the surface of the object 5 is described in the
following text.
[0078] In this context, it can be seen from FIGS. 1 and 4 that a
transmitted beam--preferably in the IR band--is transmitted by
means of a light-emitting diode 14 and is focused onto the outlet
window 7 via a deflection mirror 13 and one or more lenses 12.
[0079] The beam from the light-emitting diode thus strikes the
surface of an object 5, which is in direct contact with the window
7 of the handheld sensor, or is arranged a short distance in front
of this window.
[0080] The beams reflected from the object 5 are received again on
the same route by lenses 12, are deflected there via the deflection
mirror 13, and are passed to a receiving diode 14', which is
connected to appropriate electronics.
[0081] As soon as the receiving diode 14' identifies a reflected
transmitted beam from the proximity sensor system, this ensures
that the handheld sensor is a short distance away from the object
5, or is even touching it, and the laser diode 1 is switched on
only in this situation.
[0082] Instead of the described non-contacting scanning of the
object 5, touching scanning processes may also be used. The
arrangement of the LED 14 and photo diode 14' can then be replaced
by touching scanning of the object surface, for example by means of
a contact switch or a contact bracket, or else a pressure
sensor.
[0083] In general, the proximity identification process (operating
by touch or non-contacting) is thus intended to ensure that the
laser is switched on only when it is certain that the outlet window
7 is in contact with, or is virtually in contact with, the object
5.
[0084] In addition, a pushbutton 15 can also be arranged in the
housing 19, which is operated by manual finger pressure and on
whose operation the laser diode 1 is switched on.
[0085] This ensures that the laser diode 1 is not switched on
automatically by the proximity sensor system but that it is also
necessary to deliberately operate the pushbutton 15 as well.
[0086] In addition, a heat sink 16 for the laser diode 1 can also
be installed in the housing, preferably being in the form of a cold
wall.
[0087] A temperature stabilization element 17 can also be
installed, comprising, for example, a heating coil or a Peltier
element with an additional temperature sensor.
[0088] The temperature stabilization element 17 is intended to
ensure that the temperature of the laser diode 1 is uniform.
[0089] Once, in one preferred embodiment, the Peltier element has
cooled the laser diode 1, the heat produced by the Peltier element
must be dissipated via a further heat sink 18.
[0090] The heat sinks 16 and 18 described here are, however, not
essential to the solution, and may also be omitted if required.
[0091] The temperature stabilization element 17 may likewise also
be omitted for various applications.
[0092] In comparison with FIG. 5, it can be seen from FIG. 3 that
there is a crossing point 25 in the Y-plane (FIG. 5), so that the
focused beam 31 widens once again beyond this crossing point, thus
producing the elongated scanning bar 22.
[0093] Instead of a focusing cylindrical lens (line optics 3), a
divergent cylindrical lens may also be used, in which case the
crossing point 25 is beyond the cylindrical lens 3. The crossing
point 25 is thus virtual.
[0094] FIG. 5 also shows that the use of the chosen line optics
results in the focusing in the X- and Y-planes being at a different
height above the object.
[0095] While the focused beam 32 is focused directly on the object
in the X-axis, as is illustrated by the narrow width of the area 29
in FIG. 5, it can be seen on the other hand that the focusing in
the Y-direction is in the form of the focused beam 31 at the
crossing point 25, so that a somewhat elongated scanning bar of
length 30 and width 29 is produced beyond this crossing point
25.
[0096] This results in the advantages of a relatively high total
energy density being applied to the plane of the object 5, but
without any focusing at a single point on the plane of the object 5
or anywhere else, so that even if a human eye were to be present
instead of the object 5, there would be no need to be concerned
about damage to the retina, or any such damage would at the very
least be very greatly reduced.
[0097] The eye can no longer focus this focused beam as a point on
the retina.
[0098] The described technical teaching thus proposes a handheld
sensor in which even weakly luminescent signets (identification
features 21) can be identified with high identification accuracy,
without there being any risk of damage to a human or animal
eye.
[0099] Two different areas of the invention are claimed
independently of one another and in combination with one another,
namely the laser being switched on only when in proximity with the
object surface has been identified reliably and/or the use of line
optics which prevent point focusing on a human or animal eye
despite the use of a relatively high-energy beam. Furthermore, the
laser is switched on only when a pushbutton on the handheld sensor
has previously been activated by finger pressure.
[0100] These receiving optics have a wide aperture, that is to say
they have an f-number of approximately 1, and are therefore
particularly sensitive to light.
[0101] The laser (laser diode 1) can also be replaced by a powerful
LED or by a different radiation source or surface emitter, or even
by a superluminescence diode.
[0102] In rare cases, the line optics may also be dispensed with,
if the beam outlet already has the desired elongated surface area
of the scanning bar 22 (length 30 and width 29) and is not
coherent.
[0103] In this case, there is no need for an elongated form of
length 30, and the scanning bar 22 can also, overall, be in the
form of a round bar with a specific extent.
[0104] In order to provide a seal against external light,
additional sealing means can also be used on the head surface 26,
27 such as sealing brushes or lips or the like at the side.
[0105] Apart from this, the described proximity sensor system
results in the advantage that the laser is not switched on if the
object 5 is transparent glass. This is because the proximity sensor
system preferably reacts to diffuse reflection, and not to mirror
reflection, on the surface of the object 5.
[0106] Furthermore, the receiving element 11 in the laser
arrangement can also provide external light identification. The
laser is not switched on when external light or ambient light is
being received.
[0107] This shows that the proximity sensor system can also be
integrated in the laser optics themselves. In this case, the
elements 12, 13, 14 are omitted, and the entire proximity sensor
system is implemented by appropriate checking of the receiving
element 11.
[0108] The laser beam reflected from the object can thus also
itself be used for the proximity sensor system. In this case, only
weak, very short and absolutely harmless laser pulses are first of
all transmitted, these being used to monitor proximity. Only when
the proximity of the object is clearly identified is the same laser
raised to a more powerful laser power level, which is required in
order to identify the luminescent features.
[0109] In another refinement of the invention, however, it is also
possible to provide for a beam splitter to be arranged in front of
the receiving element 11, which splits off a specific proportion of
the laser light reflected from the object and passes this to
identification optics which evaluate the reflection, produced by
the object, of the weak, short laser pulses.
[0110] Furthermore, another variant of the invention can provide
for the receiving element 11, or a receiving element arranged in
front of the optical filter 10, not to be used for detection
purposes for proximity identification of the radiation component
reflected from the object. The proximity identification is carried
out using the photo diode 14' illustrated in FIG. 4, using the
reflected, weak and short laser pulses.
[0111] The laser is preferably pulsed in order to make it possible
to suppress as far as possible external light or ambient light
which nevertheless penetrates into the receiver. This can be done
very well by installing high-pass, low-pass or bandpass filters in
the receiver electronics, which pass only the pulse repetition
frequency of the laser. Furthermore, powerful optical filters pass
only the desired wavelength of the optical response from the
feature which has been excited optically by the laser. All other
wavelengths are suppressed, in particular including the laser
wavelength itself, which in most cases creates interference in the
receiver itself. The only situation in which the filters pass the
laser wavelength is, of course, when the response is at the same
wavelength. In this situation, a time-delayed measurement must be
carried out in order to identify the optical response from the
feature, that is to say monitoring is carried out after the end of
each laser pulse to determine whether light from the feature can
still be identified in the transmission pause. In order to suppress
external light further, the signals are additionally averaged over
a number of laser pulses. This is preferably done using a
microprocessor, after prior analog/digital conversion.
41113970.01
Drawing Legend
[0112] 1. Laser diode
[0113] 2. Focusing lens
[0114] 3. Line optics
[0115] 4. Deflection mirror
[0116] 5. Object with identification feature
[0117] 6. Transmission beams
[0118] 7. Outlet window
[0119] 8. Receiving beams
[0120] 9. Receiving lens (9': second receiving lens)
[0121] 10. Optical filter
[0122] 11. Receiving element
[0123] 12., 12'. Lenses for light probe
[0124] 13. Deflection mirror for light probe beams
[0125] 14., 14'. LED and photo diode for light probe
[0126] 15. Pushbutton
[0127] 16. Heat sink for laser diode
[0128] 17. Temperature stabilization element
[0129] 18. Heat sink
[0130] 19. Housing
[0131] 20. Optional battery or rechargeable battery
[0132] 21. Identification feature (signet)
[0133] 22. Scanning bar
[0134] 23. Arrow direction
[0135] 24. Light spot
[0136] 25. Crossing point
[0137] 26. Head surface (width)
[0138] 27. Head surface (length)
[0139] 28. Transmission beams before deflection
[0140] 29. Width (scanning bar)
[0141] 30. Length (scanning bar)
[0142] 31. Focused beam (Y-axis)
[0143] 32. Focused beam (X-axis)
[0144] 33. Beam cross section
[0145] 34. Focused beam
* * * * *