U.S. patent application number 12/293616 was filed with the patent office on 2012-02-16 for method and apparatus for optically reading information.
This patent application is currently assigned to Bayer Innovation GmbH. Invention is credited to Torsten Hupe, Stephan V+e,uml e+ee lkening.
Application Number | 20120037698 12/293616 |
Document ID | / |
Family ID | 38180682 |
Filed Date | 2012-02-16 |
United States Patent
Application |
20120037698 |
Kind Code |
A9 |
V+e,uml e+ee lkening; Stephan ;
et al. |
February 16, 2012 |
METHOD AND APPARATUS FOR OPTICALLY READING INFORMATION
Abstract
The present invention relates to a novel type of information
carrier, on which information is stored in the form of diffraction
structures. The information carrier according to the invention can
be read by being drawn manually through a reading device. The
present invention also relates to a device with which an
information carrier according to the invention can be read.
Inventors: |
V+e,uml e+ee lkening; Stephan;
(Koln, DE) ; Hupe; Torsten; (Oberhaching,
DE) |
Assignee: |
Bayer Innovation GmbH
Dusseldorf
DE
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20110121073 A1 |
May 26, 2011 |
|
|
Family ID: |
38180682 |
Appl. No.: |
12/293616 |
Filed: |
March 9, 2007 |
PCT Filed: |
March 9, 2007 |
PCT NO: |
PCT/EP2007/002060 PCKC 00 |
371 Date: |
May 12, 2010 |
Current U.S.
Class: |
235/382; 235/380;
235/457; 359/29 |
Current CPC
Class: |
G06K 19/16 20130101;
G03H 2001/2231 20130101; G11C 13/042 20130101; G03H 2001/306
20130101; G03H 1/16 20130101 |
Class at
Publication: |
235/382; 235/457;
235/380; 359/29 |
International
Class: |
G06K 5/00 20060101
G06K005/00; G03H 1/16 20060101 G03H001/16; G06K 7/14 20060101
G06K007/14 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2006 |
DE |
10 2006 012 991.1 |
Claims
1. An information carrier, wherein said information carrier
comprises data stored in the form of one or more Fourier
holograms.
2. An information carrier according to claim 1, wherein the
information carrier is a flat plastic card.
3. An information carrier according to claim 1, wherein said
information carrier comprises one or more Fourier holograms at one
level, arranged along a line.
4. An information carrier according to claim 1, wherein a plurality
of identical Fourier holograms are combined to form a larger
hologram.
5. An information carrier according to claim 1, wherein the Fourier
hologram is larger than a read spot for reading a hologram.
6. An information carrier according to claim 1, wherein markings
are applied to the information carrier which are used as a trigger
signal for a read beam and/or a detector.
7. A device for reading the information carrier according to claim
1, comprising a light source for producing a read beam, Fourier
optics, a photodetector and guide device, which restricts the
movement of the information carrier in two spatial dimensions while
the information carrier is moved in a third spatial direction in
relation to the read beam and to the photodetector.
8. A system for data transmission comprising at least one flat
information carrier, which contains data stored in the form of at
least one Fourier hologram, and at least one reading device
comprising Fourier optics, a photodetector and a guide device,
which aligns the information carrier in relation to a read beam and
to the photodetector during movement during a reading
operation.
9. A method for authentication and/or for access control comprising
utilizing a device according to claim 7.
10. A method for data transmission which comprises: (a) storing
data in the form of at least one Fourier hologram on a flat
information carrier, and (b) moving an information carrier through
a device comprising Fourier optics, a photodetector and a guide
device, which aligns the information carrier in relation to a read
beam and to the photodetector during the movement through the
device, and reading stored data.
11. A method according to claim 10, wherein the movement of the
information carrier through the device during the reading operation
is carried out by drawing said carrier through manually.
12. A method for authentication and/or for access control
comprising utilizing a device according to claim 8.
13. A method of claim 10, wherein said information carrier
comprises a plastic card.
14. A system of claim 8, wherein the information carrier is aligned
in relation to a read beam and to the photodetector as said
information carrier is drawn manually through said device.
15. An information carrier according to claim 2, wherein a
plurality of identical Fourier holograms are combined to form a
larger hologram.
16. An information carrier according to claim 3, wherein a
plurality of identical Fourier holograms are combined to form a
larger hologram.
17. An information carrier according to claim 2, wherein markings
are applied to the information carrier which are used as a trigger
signal for a read beam and/or a detector.
18. An information carrier according to claim 3, wherein_markings
are applied to the information carrier which are used as a trigger
signal for a read beam and/or a detector.
19. An information carrier according to claim 4, wherein markings
are applied to the information carrier which are used as a trigger
signal for a read beam and/or a detector.
20. An information carrier according to claim 5, wherein markings
are applied to the information carrier which are used as a trigger
signal for a read beam and/or a detector.
Description
[0001] The present invention relates to a novel type of information
carrier, on which information is stored in the form of diffraction
structures. The information carrier according to the invention can
be read by being drawn manually through a reading device.
[0002] Plastic cards as information carriers are ubiquitous
nowadays. As a consequence of increasing data processing by
machine, a person typically has a series of plastic cards with
which he can authenticate himself Examples which may be mentioned
are company identity cards, medical insurance cards, credit,
Eurocheque and debit cards.
[0003] Particularly widespread is the ID-1 format, which is
characterized in the ISO/IEC 7810 Standard ("credit card format").
It has a convenient size and can be accommodated in purses. There
are many card readers which are based on this format.
[0004] Machine-readable information can be stored on plastic cards
in various ways. For instance, optically in the form of optically
readable letters (OCR=Optical Character Recognition), bar or matrix
codes, magnetically in a magnetic strip or electronically in a
chip. However, the aforementioned storage methods only permit the
storage of a few bytes (OCR) to kilobytes (chip). The greatest
storage capacity in plastic cards is achieved nowadays by optical
memory cards.
[0005] In WO8808120 (A1) and EP0231351 (A1), optical memory cards
are described in which data is exposed photographically into a
silver halide film which is applied to the plastic cards. The data
can be written and read with a laser. In WO 8808120(A1), a device
is described with which the film can be written and read. The data
is present digitally in the form of data points. The data points
exhibit a different reflectance as compared with the surroundings
and in this way can be read with the aid of a laser beam and a
photodetector.
[0006] The disadvantage with the card and the card reader described
is that the card must be positioned exactly with respect to read
beam and detector in order to be able to read the data. In order to
read out the individual data points one after another, the card
must also be moved in relation to read beam and detector in such a
way that the read beam strikes the data points accurately. This
requires a complex card reader having a high positioning accuracy.
Moreover, the data density on the card is restricted to the
dimension of the positioning accuracy during reading. If the data
points are present more densely than the positioning accuracy of
the read beam, the individual data points can no longer be
detected.
[0007] When bar code or magnetic strip cards are used, it is
possible to draw the card through a card guide in order to read it.
The data are read as the card is drawn through manually. Mechanical
positioning of the read head in relation to the card is not
necessary.
[0008] Such a draw-through system for magnetic strip cards is
described, for example, in U.S. Pat. No. 5,128,524 (A1).
[0009] The implementation of a manual card draw-through system for
reading data which are stored on plastic cards is possible in the
case of magnetic strips and bar codes, since the data density
(quantity of bytes per unit area) is so low that the positioning of
the storage medium in relation to the read head is tolerant with
respect to the changes which occur during the manual card
guidance.
[0010] In the optical memory cards described above, the data
structures are smaller. Manual positioning of the card in relation
to the read head is therefore generally no longer possible.
[0011] However, it would be desirable to be able to read optical
memory cards having a higher storage capacity than is usual in the
case of magnetic strip or bar code cards with the aid of a card
draw-through system that can be operated manually.
[0012] Advantages of manual card guidance are, firstly, higher
convenience for the user, since he does not have to let go of the
card. and increased speed of the entire reading process associated
with this and, secondly, lower production costs of the device,
since it is possible to dispense with expensive mechanical
positioning, and also greater ruggedness of the device.
[0013] There was therefore the object of providing an optical
memory card which can be read with the aid of a card draw-through
system that can be operated manually.
[0014] Surprisingly, it has been found that this object is achieved
by the optical memory cards according to the invention described
below.
[0015] In particular, the optical memory cards according to the
invention can be read as they are drawn manually through a card
guide, although the structures which represent the data in the
storage medium are smaller than the positioning accuracy as the
card is drawn through manually.
[0016] Furthermore, the optical memory cards according to the
invention have a higher storage capacity than the memory cards
known from the prior art.
[0017] This is achieved by means of information carriers, in
particular optical memory cards, on which data are stored in the
form of Fourier holograms. Such information carriers form a first
subject of the present invention.
[0018] In one embodiment, the information (data) to be read is
present in the form of Fourier holograms on a flat information
carrier, for example a plastic card.
[0019] Suitable storage media for the hologram are all materials
which are conventional and known to those skilled in the art in
which a flat surface can be produced. Examples of this are
polymers, metals, papers, textiles, coatings, stoneware and so on,
into which the holographic structures are introduced by means of
embossing, etching, photolithography, granolithography, abrasion or
cutting. Composite materials, which are formed by combination of
the above-mentioned materials, are also conceivable.
[0020] One example of this is polymer films to which a metal film
is applied. In the case of photosensitive materials or composite
materials with photosensitive components. the holographic
structures can also be introduced by using light (silver halide
film, film made of photo-addressable polymer and so on).
[0021] A flat information carrier is understood to be an
information carrier which has a radius of curvature which is
substantially larger than the information carrier itself. Such a
flat information carrier is. for example, a credit card which has
been bent in the purse such that it has a radius of curvature of 3
m, while the card itself is only about 8 cm long and about 5 cm
wide.
[0022] The storage medium for the hologram can in this case both be
part of the information carrier itself and also merely firmly
connected to the information carrier.
[0023] The holograms can be read in reflection or transmission.
They are preferably read in reflection. To this end, a
light-reflecting surface is required, to which the hologram is
applied or into which the hologram is introduced.
[0024] The information carrier should preferably be smooth, that is
to say the roughness should be less than the holographic
structures. The roughness can be determined, for example, by means
of feeler methods (measuring instrument: KLA Tencor Alpha Step 500;
measuring method: MM-40001). The surface roughness is preferably
less than R.sub.a=10 micrometres.
[0025] The data to be stored holographically are preferably present
as a two-dimensional distribution of lightness values. One example
which may be mentioned is the data matrix code which is specified
in ISO/IEC 16022.
[0026] In the case of storing such data as a Fourier hologram, the
physical lightness distribution of the object is encoded in the
Fourier hologram in the form of angles. This is illustrated
schematically in FIG. 1: During the irradiation of the Fourier
hologram (2) with a collimated laser beam (7), the light beams are
diffracted at different angles at the hologram.
[0027] Fourier holograms are known and their properties are
described, for example, in P. Hariharan, Basics of Holography,
Cambridge University Press, 2002, pages 8 to 10.
[0028] With the aid of Fourier optics, the angles can be led back
into location information again (FIG. 1 and FIG. 2): The beams
diffracted at the same angle are focused at a point by the Fourier
lens (5). The beams diffracted at different angles are focused at
different points by the Fourier lens.
[0029] The points can be imaged on a detector, for example a
camera, and can thus be processed further electronically.
[0030] One important property of the Fourier holograms in
combination with Fourier optics is that the points imaged on the
detector are not displaced if the hologram is displaced at right
angles to the incident laser beam. Only the intensity of the image
on the detector changes. This is illustrated in FIG. 2: If the
Fourier hologram (2) is moved through the reader (7), an image
appears on the detector as soon as the read beam strikes the
hologram partly. The intensity (brightness) of the image rises
until the read beam is irradiating the entire hologram and then
decreases to zero again until the read beam is no longer
illuminating the hologram.
[0031] Surprisingly, it has been established that this effect can
be used to read information which is stored on a flat information
carrier in the form of Fourier holograms while the information
carrier is being displaced in relation to an incident laser beam,
that is to say, for example, is being moved manually through a
guide.
[0032] If the hologram is registered only partially by the read
spot, then the image is less bright and less sharp than if the
entire hologram is registered by the read spot. From this, it could
easily be concluded that it is particularly beneficial to configure
the read spot to be larger than the hologram in order that, during
the reading process, as many regions of the hologram as possible
are always registered by the read spot. However, this is not the
case. If the read spot is larger than the hologram, then parts of
the information carrier which do not have a hologram are also
always illuminated. As a result, in general fewer light beams are
deflected at the hologram, so that the brightness decreases. In
addition, scattering effects as a result of irradiating the
information carrier outside the hologram lead to increased
background noise on the detector.
[0033] Surprisingly, it has been found that the imaging properties
during irradiation of the hologram are particularly good if the
read spot is smaller than the hologram. The read spot is
particularly preferably 0.9 to 0.1 times as large as the
hologram.
[0034] Particularly good imaging properties are achieved if a
plurality of holograms having the same content is placed directly
on one another to form a larger hologram. Particularly preferably,
2 to 9 holograms with the same content are placed directly on one
another and therefore form an enlarged hologram.
[0035] The geometry of the Fourier holograms is preferably matched
to the profile of the read spot. Conventional lasers as a source of
the read beam produce a circular or elliptical read spot, in which
the intensity decreases from the inside towards the outside.
[0036] Particularly good images are obtained if four holograms with
the same content are assembled to form a larger hologram, of which
only a central circular or elliptical region which is somewhat
larger than the read spot is applied to the information carrier, as
illustrated in FIG. 4: FIG. 4(a) shows a Fourier hologram. This is
quadrupled in FIG. 4(b), the four identical holograms being
arranged in the form of a rectangle. In FIG. 4(c) the enlarged
hologram is cut in such a way that the hologram has the shape of
the read spot. For the purpose of better illustration, in FIG. 4
the individual holograms are provided with a black frame, which,
however, does not actually occur.
[0037] The size of the holograms is preferably 0.1 to 5 mm in
diameter.
[0038] A further subject of the present invention is a device for
reading the optical memory cards according to the invention.
[0039] Such a device comprises a light source for a read beam,
Fourier optics, a photodetector and a guide device which aligns the
information carrier in relation to the read beam and to the
photodetector during the movement during the reading operation, in
particular when being drawn manually through the device. The guide
restricts the movement of the information carrier in two spatial
dimensions, while the information carrier is moved in the third
spatial direction. The information carrier is, for example, moved
manually through the guide and in the process is illuminated with a
light beam. The light beam is diffracted at the Fourier hologram of
the information carrier, and the diffracted beams are imaged with
the aid of Fourier optics onto a detector, where the optical signal
is transformed into an electronic signal.
[0040] By using the device according to the invention, the optical
memory cards according to the invention can be read in transmission
and/or reflection.
[0041] One example of an embodiment of such a device, with which
memory cards can be read in reflection, is illustrated in FIG. 3.
It comprises two guide rails (10 and 11), between which the
information carrier (1) is moved manually. One of the guide rails
(10 here) has a roller (12), which is mounted with a pressure
spring (13) and presses the information carrier (1) against the
other rail (11 here) as it is drawn through manually. The roller is
tilted slightly, so that an information carrier is pressed
downwards automatically as it is drawn through. Therefore, as it is
drawn through manually, the information carrier is pressed both
against a rail (11 here) and also against the base of the guide.
Therefore, two of the three possible spatial directions are
restricted. The information carrier is moved in the third spatial
direction, parallel to the guide rails 10 and 11.
[0042] In the process, it sweeps over the read beam (7), which is
incident through a hole (16) in one of the guide rails (11 here).
The hole (16) is arranged at the level of the hologram (2) on the
information carrier (1). At the same height, a groove (15) is
preferably milled in the rail which faces the hologram and in which
the hole is located, the said groove preventing a hologram located
on the information carrier from being gradually scratched as it is
drawn repeatedly through the guide.
[0043] A detector (14) is preferably inserted into the guide and
detects whether an information carrier is being moved through the
guide. For instance, use can be made of a forked light barrier,
whose light beam is interrupted by the information carrier. The
interruption of the light beam from the light barrier can be used
as a trigger for the read beam (3) and the detector (camera) (6).
As soon as the light barrier is interrupted, the read beam is
switched on and the image on the camera is evaluated.
[0044] It is also possible to switch the camera on with a defined
time delay in relation to the read beam.
[0045] It is likewise possible to use a plurality of light
barriers.
[0046] It is also possible for a plurality of holograms to be read
one after another. The holograms are then arranged on the
information carrier at one level, along a line (9) in the storage
medium (17).
[0047] In the event that a plurality of holograms, which are
arranged along a line, is used on an information carrier, it is
conceivable, in addition to the holograms, also to insert markings
into the information carrier and/or the storage medium, which
markings function as a trigger for the camera and/or the read beam.
In this way, it is easily possible to signal to the camera when a
new hologram is being imaged.
[0048] Furthermore, the use of the aforementioned device as a card
reader for information carriers in the form of plastic cards of all
types (bank cards, credit cards, identity cards, etc.) is also the
subject of the present invention.
[0049] A further subject of the present invention is a method for
data transmission which comprises (a) storing the data in the form
of at least one Fourier hologram on a flat information carrier, for
example a plastic card, and (b) moving the information carrier
through a device comprising Fourier optics, a photodetector and a
guide device, which aligns the information carrier in relation to
the read beam and to the photodetector during the movement through
the device, and reading the stored data in this way. The movement
of the information carrier through the device during the reading
operation is preferably carried out by drawing it through
manually.
[0050] A further subject of the present invention is a system for
data transmission comprising at least one flat information carrier,
for example a plastic card, which contains data stored in the form
of at least one Fourier hologram, and at least one reading device
comprising Fourier optics, a photodetector and a guide device,
which aligns the information carrier in relation to the read beam
and to the photodetector during the reading operation, in
particular as it is drawn manually through the device.
[0051] Such a system can be used for a large number of
applications, for example for the authentication of persons or
goods or access control to buildings or rooms.
DESIGNATIONS RELATING TO THE FIGURES
[0052] 1 Information carrier (plastic card)
[0053] 2 Fourier hologram
[0054] 3 Light source with collimation optics
[0055] 4 Beam splitter
[0056] 5 Fourier lens
[0057] 6 Detector (camera)
[0058] 7 Collimated light beam (read beam)
[0059] 8 Image on the camera
[0060] 9 Line along which holograms can be stored
[0061] 10 Guide rail 1
[0062] 11 Guide rail 2
[0063] 12 Roller
[0064] 13 Pressure spring
[0065] 14 Detector (forked light barrier)
[0066] 15 Groove
[0067] 16 Hole for read beam
[0068] 17 Storage medium
* * * * *