U.S. patent application number 09/194318 was filed with the patent office on 2002-09-05 for personal identification.
Invention is credited to GIFFORD, MAURICE MERRICK, MCCARTNEY, DAVID JOHN, SEAL, CHRISTOPHER H..
Application Number | 20020122572 09/194318 |
Document ID | / |
Family ID | 27238606 |
Filed Date | 2002-09-05 |
United States Patent
Application |
20020122572 |
Kind Code |
A1 |
SEAL, CHRISTOPHER H. ; et
al. |
September 5, 2002 |
PERSONAL IDENTIFICATION
Abstract
A handheld imaging apparatus (125) for capturing an image of an
eye (110) comprises a housing (125) having an eyecup (115) at a
rear window (120) to position the eye. The housing (125) provides a
lineofsight through the apparatus to a front window (140). An
angled, semireflecting mirror (145) in the line of sight directs an
image of the eve to a camera (135) for the purposes of image
capture. The apparatus also includes a transmitter (160) and a
receiver (162) to transmit and receive data relating to iris image
information to and from a remote apparatus.
Inventors: |
SEAL, CHRISTOPHER H.;
(SUFFOLK, GB) ; MCCARTNEY, DAVID JOHN; (SUFFOLK,
GB) ; GIFFORD, MAURICE MERRICK; (IPSWICH,
GB) |
Correspondence
Address: |
NIXON & VANDERHYE
1100 NORTH GLEBE ROAD
8TH FLOOR
ARLINGTON
VA
222014714
|
Family ID: |
27238606 |
Appl. No.: |
09/194318 |
Filed: |
July 21, 1999 |
PCT Filed: |
June 6, 1997 |
PCT NO: |
PCT/GB97/01524 |
Current U.S.
Class: |
382/117 |
Current CPC
Class: |
A61B 3/1216 20130101;
G06V 30/142 20220101; G06V 40/19 20220101; G06V 10/143 20220101;
G07C 9/37 20200101 |
Class at
Publication: |
382/117 |
International
Class: |
G06K 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 6, 1996 |
GB |
9611787.4 |
Oct 18, 1996 |
GB |
9621900.1 |
Apr 15, 1997 |
GB |
97302580.2 |
Claims
1. An apparatus for providing an information signal characteristic
of an eye, said apparatus being arranged to be carried into an
operative position by a user, said apparatus comprising: a housing;
a wave source mounted on the housing, and operable to provide waves
to be incident upon the surface of the eye over an area outside the
pupil; an image capture device mounted on the housing, and operable
to provide an image signal representing one or more features of the
anterior of the eye responsive to waves reflected from the eye; and
a transmission device operable to transmit said information signal
derived from said image to a remote apparatus.
2. An apparatus according to claim 1 wherein: said housing has an
entrance window; said wave source comprises an illumination source
operable to illuminate the eye; and said image capture device is
mounted within the housing and is in optical communication with
said entrance window.
3. Apparatus according to claim 1 or 2, wherein the apparatus is
adapted to be held in the hand.
4. Apparatus according to any preceding claim, wherein said
transmission device comprises a cordless transmission means.
5. Apparatus according to any one of claims 2 to 4 further
comprising a target object visible, in use, to the eye to
facilitate alignment of the eye with said entrance window.
6. Apparatus according to claim 5 wherein said target object
comprises a further window, in optical communication with the
first-mentioned window to provide a view beyond the housing to the
eye.
7. Apparatus according to claim 5 or 6 wherein said target object
comprises a visual display means which, in use, is visible to the
eye.
8. Apparatus according to any one of claims 5 to 7 wherein said
image capture device is responsive to light reflected from the eye
which differs in spectrum from light from said target object.
9. Apparatus according to claim 8 wherein said image capture device
is responsive to non-visible light.
10. Apparatus according to claim 9 wherein said image capture
device is responsive to near infra red light.
11. Apparatus according to any one of claims 8 to 10 wherein: said
apparatus further comprises a wavelength selective reflector
effective to reflect either said visible light or said light of a
different spectrum and to allow passage of the other; wherein, in
use, visible light travels along a first optical path from the
target object via the wavelength selective reflector to the eye and
light travels along a second optical path from said illumination
source via said wavelength selective reflector to said image
capture apparatus.
12. An apparatus according to claim 9 or 10 further comprising an
optical element interposed between said eye and said target object,
said element being substantially transparent to non-visible
radiation, and comprising a first region which is more transparent
to visible optical radiation than a second region thereof.
13. An apparatus according to claim 12 wherein said first region is
surrounded by said second region.
14. An apparatus according to any preceding claim further
comprising an encoding means arranged in operation to encode at
least part of said image signal to provide said information signal,
whereby said information signal is of lesser extent than said image
signal.
15. Apparatus according to claim 14, wherein the encoding means is
arranged to encode at least an iris portion, or part thereof, of a
captured image.
16. Apparatus according to claim 15, wherein the encoding means is
arranged to encode one or more further features of the eye or
surrounding face.
17. Apparatus according to any one of claims 14 to 16 wherein the
means for encoding is controllable to select one or more of a
plurality of encoding algorithms.
18. Apparatus according to any preceding claim further comprising
means to encrypt said encoded information.
19. Apparatus according to any one of claims 2 to 18, further
comprising means to operate the illumination source in a pulsed
manner.
20. Apparatus according to any one of claims 2 to 19 wherein said
illumination source comprises a plurality of light sources emitting
light in respective different wavelength bands.
21. Apparatus according to claim 20 wherein said sources are
controllable individually to illuminate an eye(s) for information
capture.
22. Apparatus according to any one of the preceding claims, further
comprising receiving means to enable bidirectional communications
with said remote apparatus.
23. Apparatus according to claim 22, wherein one or more of the
functions of the said apparatus is controllable by the remote
apparatus.
24. Apparatus according to any preceding claim, further comprising
means to select at least one image from a plurality of sequentially
captured images for further processing.
25. Apparatus according to any one of the preceding claims, wherein
said image capture device has a fixed focal length.
26. Apparatus according to any preceding claim further comprising
means for locating an eye in predetermined relation to said
entrance window.
27. Apparatus according to any preceding claim further comprising a
trigger means operable by said remote apparatus.
28. Apparatus according to any one of the preceding claims,
provided with means to read data from a personal identity card.
29. Use of an apparatus according to any one of the preceding
claims to identify or verify a human.
30. Use of an apparatus according to any one of the preceding
claims to identify or verify an animal.
31. A method of identifying a human or an animal, said method
comprising: (a) capturing an image of an eye of the human or
animal; (b) encoding said image to form a code of at least an iris
portion, or part thereof, of the eye; and (c) transmitting said
code to a remote apparatus in a cordless manner.
32. An imaging apparatus substantially as hereinbefore described
with reference to any one or more of the accompanying drawings.
33. An apparatus for capturing information characteristic of one or
both of a user's eyes, the apparatus comprising: a) a housing
having a window; and b) means for locating one or both of the
user's eyes in predetermined relation to the window, wherein the
housing is provided with: d) means for illuminating the eye(s); f)
means for capturing information characteristic of the eye(s); and
d) means for transmitting the information to remote apparatus.
34. Apparatus according to claim 33, wherein the housing is
provided with a further window, in optical alignment with the
first-mentioned window which provides to the user in use of the
apparatus a view beyond the housing.
Description
[0001] The present invention relates to personal identification and
apparatus, methods and uses therefor.
[0002] In today's world of electronic communication and commerce,
the ability to identify a person for the purposes of security in
remote transactions is paramount. A common form of security is a
simple password which, for example, is entered when a user wishes
to access a computer network. Another form of security, which is
widely used in bank automatic teller machines (ATMs), is a personal
identification card, which holds on a magnetic strip encoded
information such as the owner's personal details and account
number, which is used in combination with a personal identification
number (PIN) entered by the user when the transaction is
initiated.
[0003] Various ways have been demonstrated of fraudulently
by-passing the above-described and other commonly used security
measures to gain access to private information or resources. Such
security problems are discussed in the article entitled "Industrial
Cryptography" in the IEE Review dated May 1996. As the title
suggests, this article focuses on how cryptography can be used
effectively as a way of increasing security.
[0004] Another way of ensuring the identity of a person is to
capture and encode a biometric from the person and compare the
result with a previously-stored, or enrolled, result, for example
stored on a remote database system. A biometric, for the present
purposes, is a statistical or quantitative measure of a biological
feature of a person. The most well-known biometric for humans, used
for identification purposes, is the fingerprint. A `robust`
biometric, such as a fingerprint, is one which can be used reliably
and repeatedly to identify a person.
[0005] Recently, the use of the iris of an eye as a robust
biometric for identification purposes has been proposed. U.S. Pat.
No. 5,291,560, dated Mar. 1, 1994, describes a method of encoding
the image of an iris into a 256-byte iris code. It has been shown
that such a code can be used as a very reliable personal
identifier.
[0006] One proposed example of the use of an iris code is for
identifying a customer attempting to withdraw cash from an ATM
(automatic teller machine). The proposed ATM includes an imaging
system which comprises a window through which the customer looks
and an auto-focusing camera. The camera is positioned directly in
the line of sight of the customer. When the customer looks through
the window and, for example, inserts his bank card into the ATM,
the camera captures an image of his eye.
[0007] Once the system has captured a suitable representation of an
eye, the representation is digitised (if not already in digital
form) and encoded to form an iris code. This iris code can then be
compared with a stored iris code of allegedly the same person. If
the two codes are sufficiently similar, the identity of the
customer is verified and cash withdrawal, for example, is
permitted.
[0008] This system is designed to be non-intrusive and can be used
by anyone wishing to withdraw money from the ATM.
[0009] A problem arises in relation to such systems in that the
apparatus is fixed and the customer must move his head relative to
it so that the apparatus can capture an image of his eye. He must
position his head such that the captured image is in focus and
contains sufficient detail of the iris. Hence, if a fixed focus
image capture device is employed the customer must position himself
at the correct distance from the apparatus. This makes use of the
apparatus awkward. This problem can be alleviated to an extent by
providing an image capture device having an auto-focus and
auto-zoom facility, but that results in the apparatus being bulky
and expensive to manufacture.
[0010] An alternative approach is disclosed in U.S. Pat. No.
5,369,669. This patent discloses a mobile retinal scan identifier.
Although the apparatus is easier to use than fixed apparatuses it
uses scanning optics and is therefore both complex and expensive to
manufacture.
[0011] In accordance with a first aspect of the present invention
there is provided an apparatus for providing an information signal
characteristic of an eye, said apparatus being arranged to be
carried into an operative position by a user, said apparatus
comprising:
[0012] a housing;
[0013] a wave source mounted on the housing, and operable to
provide waves to be incident upon the surface of the eye over an
area outside the pupil;
[0014] an image capture device mounted on the housing, and operable
to provide an image signal representing one or more features of the
anterior of the eye responsive to waves reflected from the eye;
and
[0015] a transmission device operable to transmit said information
derived from said image to a remote apparatus.
[0016] In known iris recognition apparatuses the information
captured comprises an optical image of the eye. However, it is
envisaged that other forms of information characteristic of the
eye, for example reflected sound-wave patterns, could be used to
uniquely identify different eyes. Thus, even though the following
description refers in general to captured optical images, it will
be appreciated that this is for convenience only, and that
embodiments employing the capture of other types of information are
intended to fall within the scope of the present invention.
However, embodiments using optical image capture are preferred.
[0017] By providing an apparatus which captures an image of an
anterior part of a person or animal's eye (e.g. iris, cornea,
sclera, eyelids etc.) the need for scanning optics is removed. This
results in the apparatus being less bulky and less expensive than
known apparatuses. If the eye to be investigated is that of the
user, then since the user carries the apparatus to an operative
position, rather than moving his eye into a suitable position for
the apparatus, the apparatus is easier to use. The apparatus might,
for example, form part of a mobile phone, or it might be worn on
the wrist or as part of a pair of glasses. The waves produced by
the apparatus may be incident both on the pupil as well as an area
outside the pupil.
[0018] It is, of course, possible that the apparatus will be used
by one person to obtain an information signal characteristic of
another person's eye. In this way the apparatus might be useful,
for example, to a policeman who wishes to identify or verify the
identity of a person he has apprehended. The embodiments set out
below involve the user using the apparatus on his own eye. However,
it is to be understood that the eye under investigation may be that
of a person or animal other than the user.
[0019] Preferably, the apparatus is adapted to be held in the hand
and can therefore be held by the user and brought towards his or
another's eye in use. Being portable, the apparatus need not be
associated with any one particular system or remote apparatus and,
indeed, may be used with various different types of remote
apparatus.
[0020] The transmission device may comprise a cordless transmission
device. This arrangement has the advantage that the user does not
need to concern himself with physical cable connections, for
example on the back of a PC. Also, a user is not so restricted in
his position relative to the PC, or other remote equipment, during
use of the apparatus. Various types of cordless link, for example
an ultrasonic, optical or RF link might be used.
[0021] An alternative communications link between the apparatus and
the remote apparatus might comprise a telephone line, or similar
connection. In this case, the apparatus includes means to convert
electrical iris code data to an audible signal to be transmitted
along the telephone line. The means to convert between sound and
electrical data might employ standard modem technology.
[0022] Preferably, the apparatus comprises a target object viewable
by the person whose eye is being investigated.
[0023] In preferred embodiments, the target object comprises a
second window which provides a "line-of-sight" for the user,
through the first window, to allow the user to view the environment
beyond the apparatus. The second window may be a simple opening in
the housing or might possibly include a visual display.
[0024] Having a second window is particularly advantageous when
combined with a cordless arrangement, since the user is able to see
accurately where the apparatus is pointing whilst looking into the
apparatus for the purpose of eye image capture: the user can direct
the apparatus appropriately at the remote apparatus receiver. It is
believed also that allowing the user to fixate on the remote
equipment causes the pupil of the eye to contract thus providing a
larger and clearer view of the iris. Also, to a large extent, the
view through the second window can provide a means for aligning the
eye correctly in relation to the imaging means. However, further
means to aid alignment, for example cross-hairs, may be
provided.
[0025] The second window may be employed to allow a user to view a
remote screen on which one or more captured images of the eye are
displayed. The benefit to the user in this case is that he can see
on the screen substantially what the imaging means is seeing, and
adjust his eye position for correct alignment if necessary. In this
case the imaging means might be a video camera which is capable of
transmitting real time images of the eye to the screen.
[0026] In preferred embodiments, said image capture device is
responsive to user light reflected from the user which differs in
spectrum from light from said target object. This arrangement
allows the use of wavelength dependent optical devices to interact
differently with user light and light from the target object.
[0027] The apparatus preferably comprises an encoding means for
encoding captured information prior to its transmission. This has
the advantage that the signal transmitted from the apparatus
requires less bandwidth (assuming the transmission is to be
achieved in a given time) than would be required by the
transmission of the image signal.
[0028] The encoding means is preferably arranged to encode at least
the iris portion, or part thereof, of a captured image. The
encoding means may also encode one or more further features of the
eye or surrounding face. For example, the code might include
details of the pupil, the cornea, the sclera, and/or the eyelids,
etc.
[0029] In preferred embodiments, the imaging apparatus further
comprises means to encrypt an encoded image.
[0030] Encryption makes the apparatus more secure in use. The
encrypted image code data typically includes other encrypted data
such as date, time, apparatus serial number and/or even a GPS
(global positioning system) co-ordinate record.
[0031] Such extra information, when held in encrypted form, further
increases the security of the system. For example, an encrypted
code including encrypted time and date information could be
intercepted by an eavesdropper but could not easily be used again
since the date and time combination would be unique.
[0032] The apparatus may further comprise receiver means to enable
bidirectional communications with the remote apparatus. Preferably
then optical communications can be utilised using, for example,
infra-red transmitters and receivers (e.g. photo-diodes). Such a
`cordless` arrangement might be used with remote apparatus having a
suitable optical transmitter and receiver arrangement.
[0033] The illumination means preferably provides substantially
non-visible wavelengths of optical radiation, for example
predominantly near-infra-red (NIR) or infra-red (IR) optical
radiation. A substantially non-visible illumination source is
believed to be more comfortable to the user. Also, in a
line-of-sight embodiment, a substantially non-visible illumination
source detracts the user's attention less from the line-of-sight
image of the surroundings than would a source of visible optical
radiation. For convenience only, the term "light" is intended in
this description to include non-visible wavelengths of optical
radiation. For this reason, the terms "light" and "optical
radiation" are interchangeable.
[0034] In embodiments of the invention, correct eye alignment may
be achieved by providing an optical component having a major region
which is relatively less transmissive to visible optical radiation
than a minor region of the component. The minor region would
preferably be situated near or at the centre of the window and
would be sufficiently small to require the pupil of an eye to be
positioned close to the entrance window, in alignment with the
minor region, to see a reasonable field of view of, for example,
the target equipment through the apparatus. Then, in use, the
person looking through the window would be encouraged to align the
pupil of their eye with the minor region of the window thereby
ensuring that the iris of the eye would be substantially centrally
positioned and thus correctly aligned with respect to the window
for the purposes of image capture. Also, to some extent,
appropriate sizing of the minor region would control the distance
the user places his eye from the screen. This would be beneficial
in terms of reducing or removing any need to focus the imaging
means.
[0035] The minor region of the window may comprise a material
having a different optical composition from the major region. The
major region might be substantially transparent to visible optical
radiation and comprise, for example, clear glass or plastics
material. Alternatively, the minor region may simply be a hole
appropriately positioned in the window material of the major
region. The major region might comprise, for example, a gelatin
filter which is transparent to IR and NIR radiation.
[0036] Preferably, when using non-visible wavelengths of optical
radiation, for example IR or NIR radiation, for the purposes of eye
illumination and image capture, the window is substantially
uniformly transparent over the window area to those wavelengths.
Thus, while the window has only a minor region suitable for
viewing, and thus aligning, purposes, the whole area of the window
can be used for image capture purposes.
[0037] The apparatus preferably includes a trigger means. The
trigger means may be operable by the user, by the apparatus itself
or even, in a bidirectional embodiment, by the remote apparatus.
Such arrangements allow the user, or one of the said apparatuses,
to control exactly when image capture and/or when data transfer
occurs. This feature finds particular application when using a
cordless arrangement.
[0038] As well as being used to identify humans, the present
apparatus can be used, in an appropriate form, to identify animals.
Such an apparatus would typically need to be larger (depending on
the size of the animal's eyes) and more robust. Suitable candidates
for such a use are, for example, horses, and in particular
expensive race-horses.
[0039] Embodiments of the present invention will now be described,
by way of example only, with reference to the following drawings,
of which:
[0040] FIG. 1 is a schematic representation of an imaging
apparatus;
[0041] FIG. 2 is a schematic diagram which illustrates one possible
hardware architecture for the imaging apparatus;
[0042] FIG. 3 is a flow chart of an image capturing and encryption
process;
[0043] FIG. 4 is a diagram which illustrates possible
configurations of illumination source;
[0044] FIGS. 5a and 5b are diagrams which illustrate correct and
incorrect eye alignments respectively; and
[0045] FIG. 6 is a diagram which illustrates an arrangement of
apparatus to overcome the incorrect alignment illustrated in FIG.
5b.
[0046] FIG. 1 illustrates the imaging apparatus in use. The imaging
apparatus is principally intended to be used by a single user and
is thus designed to be intrusive, requiring a user to place his eye
(and surrounding face) directly in contact with the apparatus. In
the event it is intended that more than one user will use the
apparatus, personal, replaceable eye-cups can be provided.
[0047] The apparatus is contained in a suitable housing 125. A user
positions his eye 110 by placing his face appropriately against an
eye-cup 115 at a rear window 120 of the housing 125. The eye-cup
acts both as a means of minimising the amount of ambient light
entering the apparatus and as the means for aligning the user's eye
with the window.
[0048] The eye-cup 115 is attached to a barrel 130 formed in the
housing 125 which provides a fixed separation between the eye 110
and a fixed-focus Charge Coupled Device (CCD) camera 135. The
length, however, of the barrel 130 is adjustable to suit different
users and is lockable once the correct length has been determined.
The barrel 130 also provides a line-of-sight for the user, from the
rear window 120 to a front window 140, through the housing 125. The
adjustable barrel and fixed focus camera arrangement may be
replaced by an auto-focusing camera arrangement. However, such an
arrangement would increase the optical, electronic and mechanical
apparatus complexity.
[0049] The optical path between the eye 110 and the camera 135
subtends an angle of 90.degree. due to a partially reflecting,
45.degree. mirror 145 in the line-of-sight of the barrel 130.
[0050] An infra-red (IR) illumination source 150 is located between
the mirror 145 and the eye 110 to illuminate the eye. The source
has an associated screen 155 to prevent light travelling directly
from the source 150, via the mirror 145, to the camera 135.
[0051] An IR transmitter 160 and receiver 162 are located on the
front of the housing 125, in line with the line-of-sight of the
barrel 130, and a trigger button 165 is included on the housing for
the user to control when the image is captured and/or transmitted
to a remote apparatus (not shown).
[0052] As has already been mentioned, the connection between the
apparatus and the remote apparatus might instead comprise a
telephone line or similar connection, and the apparatus might then
employ known modem technology to facilitate data transfer across
the telephone line to and from the remote apparatus.
[0053] The front of the barrel 130 includes an IR filter 170 to
minimise the amount of stray IR radiation that enters the
apparatus. Additionally, the filter 170 might be useful to protect
the user's eye from the accidental reflection of radiation emitted
from the output of the transmitter 160. The CCD camera 135 is
protected from stray visible light with a visible light filter 175
positioned between the camera and the barrel. The CCD camera is a
standard black and white camera which is also sensitive to IR
optical radiation. Other types of camera, for example a colour
camera, could equally be used for image capture.
[0054] The apparatus also includes appropriate electronic circuitry
180 contained in the housing (described in more detail in relation
to FIG. 2.).
[0055] An optical indicator 185 is positioned in the barrel, in the
field of view of the user. The indicator comprises one or more LEDs
of varying coiours which can be illuminated to indicate different
apparatus statuses (as described below). Other indication systems
which will be apparent to the skilled person may provide effective
solutions. For example, these might include the use of display
panels and/or sound.
[0056] In practice, the two filters 170 and 175 may be replaced by
crossed polariser screens to prevent stray and unwanted light from
outside the apparatus reaching the camera 135. The polarisers would
be positioned in a similar fashion to the filters. The nature of
the filters or polarisers depends on the type of illumination used.
For example, if the imaging wavelength is near infra-red (NIR) or
IR then an IR filter is required to prevent stray IR radiation from
entering the apparatus through the front window 140. Alternatively,
if the imaging wavelengths) is that of visible light then crossed
polarisers over the front window 140 and the camera 135 could be
used. Other similar light blocking or filtering arrangements, which
will be apparent to the skilled person, may provide equally
effective solutions.
[0057] A `hot mirror` 145 (for example, as sold under catalogue
number 35-6681 by Eaiing Optics of Greylaine Rd, Watford, U.K.) is
located directly above the CCD camera 135. The mirror 145 slopes
downwardly and forwardly at 45.degree. to the longitudinal axis of
the barrel 130. The mirror is formed from a glass slide having a
coating of dielectric materials on its underside. The other side of
the glass slide is coated with an anti-reflective coating 147. The
coating 146 of dielectric material is effective to reflect
approximately 80% of near infra-red light which falls upon it and
to allow the passage of approximately 90% of visible light which
falls upon it.
[0058] An advantage of this type of mirror is that, to some extent
at least, the mirror also acts as a filter to IR radiation reaching
the eye and to visible light reaching the camera. Other forms of
lens, filter, beam splitter and/or prism arrangement could be
used.
[0059] The overall size of the apparatus depends mainly on the size
of the opening for the eye 120 and on the level of comfort and ease
of use required by a user of the apparatus. The hardware for the
apparatus is designed onto a single application specific integrated
circuit (ASIC) chip, the size of which is not a limiting factor to
the size of the apparatus. Also, known CCD cameras can have
dimensions in the order of millimeters and are not a limiting
factor of the apparatus size.
[0060] Although FIG. 1 shows the line-of-sight of the imaging
apparatus as being directly through a barrel, it will be
appreciated that the line-of-sight may instead be via path bending
optics such as mirrors or prisms and may include lenses. Such
arrangements may provide for an even more compact design and may
enhance the image of the outside environment received by the user
or the image of the eye received by the camera.
[0061] In FIG. 1, the line of sight is an optical path through the
barrel. It is envisaged, however, that the line of sight could be
provided by a screened image of the environment beyond the
apparatus, for example, on an liquid crystal display (LCD) screen.
The image could be provided by a CCD camera mounted on the front of
the apparatus. Thus, it would be possible to superimpose graphical
indicators onto the image to aid the user in aligning the said
apparatus with the remote apparatus. Alternatively, the LCD screen
may be substantially transparent, to allow the user to see the
actual environment beyond the apparatus, and the screen could be
used purely for superimposing alignment, or other, information over
the actual image. Correct alignment could be established by
monitoring a series of signals being emitted by one of the imaging
apparatus or the remote apparatus and being received and processed
by the other. Although such an arrangement is technically more
complex than a simple line-of-sight arrangement through a barrel,
as electronic devices such as CCD cameras and LCD displays become
smaller and cheaper, such a technically more complex arrangement
might make more practical sense. The LCD might alternatively echo
the image signal output by the image capture apparatus.
[0062] FIG. 2 shows one possible hardware architecture arrangement
for the apparatus. As already stated, the processing hardware is
preferably engineered onto a single ASIC chip. The apparatus is
controlled by a processor 200 which runs software held in read-only
memory (ROM) 205. The processor 200 is connected via a bus 210 to
the ROM 205, a block of random access memory (RAM) 215 and an
input/output (110) controller 220. The RAM is large enough to hold
at least one captured image of an eye. The I/0 controller 220 is
connected by appropriate circuitry and drivers (not shown) to the
IR transmitter 160 and receiver 162, the CCD camera 135, the
trigger 165, the IR illumination source 150 and the optical
indicator 185. The whole apparatus is powered by a suitable battery
(not shown).
[0063] The processor 200 is sensitive to signals received from the
trigger 165, the IR receiver 162 and the CCD camera 135. Also, the
processor controls the IR transmitter 160, the IR illumination
source, the CCD camera operation and the optical indicator 185.
[0064] The flow diagram in FIG. 3 illustrates one possible process
for the image capturing, processing and transmitting aspects of a
user validation system. This procedure includes encryption to
enhance the level of security. The encryption system uses a `public
key` to encipher data and a private key (known only to the
recipient of the enciphered data) to decipher the data.
[0065] In step 300, the imaging apparatus is in a state where a
trigger depression is awaited to start the process. When the user
presses the trigger, the trigger generates a signal which is
received by the processor. The processor then controls the IR
transmitter to send a signal, in step 305, to the remote apparatus
to initiate communications. In response, the remote apparatus sends
a return message to the imaging apparatus.
[0066] In other embodiments, the trigger is substituted by the
imaging apparatus, or the remote apparatus, monitoring for correct
alignment. When correct alignment is established by the user, the
capture, encoding and transmitting operations are initiated.
Monitoring would involve one or other of the apparatuses emitting a
signal which could be received and processed by the other apparatus
to indicate correct alignment.
[0067] If the return message is not received by the imaging
apparatus in step 315, for example as a result of the remote
apparatus not receiving the first signal, the optical indicator
lights up red in step 320 to indicate failure and inform the user
to re-start the process by pressing the trigger again.
[0068] If the return message is received in step 315, the signal
from the remote apparatus includes a selection of which public
encryption key and which iris code format the imaging apparatus
must use for successful transmission. A plurality of public
encryption keys and a plurality of iris code algorithms from which
the selection can be made are stored in the RAM (or the ROM) in the
imaging apparatus. The remote apparatus also transmits a date and
time stamp to the imaging apparatus.
[0069] The information in the return signal, transmitted by the
remote apparatus, is stored in the RAM in the imaging apparatus for
subsequent access.
[0070] Next, in step 325, the processing means signals to the
camera that one or more images should be captured. The images which
are captured are stored in the RAM. In step 330, the processing
means determines if the stored image, or which image, is suitable
for encoding. If the, or none of the, images is/are suitable, the
processor signals to the camera to re-capture the image(s).
[0071] The image capturing step includes control of the
illumination source. The illumination source is connected in a
control loop whereby the processor can vary the light intensity of
the source depending on, for example, the colour of the user's
iris: a light blue iris reflects far more light and needs less
illumination than a dark brown iris. Several sequentially captured
images, similar to a video sequence, might be required for the
processor and software to determine the optimum illumination for
the eye before a suitable image, or suitable images, is/are
obtained.
[0072] It is suggested that pulsing the illumination source is more
desirable than using a continuous source, although the image
capture would need to be synchronised with a pulse of light to
ensure suitable illumination. Pulsing light has the advantage that
the user's eye is exposed, on average, to less optical radiation.
Also, a pulsed source uses less energy.
[0073] Capturing multiple images can also overcome problems such
as, for example, the user blinking at the point when one image is
captured. Known digital signal processing techniques can be used to
establish which image is the best and to reject unsuitable
images.
[0074] When a suitable image is obtained, the image data is
retrieved from the RAM and is processed to form an iris code, in
step 335, using the iris code generating algorithm selected by the
remote apparatus in step 315. An example algorithm is that
described in U.S. Pat. No. 5,291,560. The resulting iris code is
stored in the RAM.
[0075] The processor then encrypts the iris code, in step 340,
using the selected public key, along with the date and time stamp
provided by the remote apparatus in step 315. The resulting data is
stored in RAM. The coded and encrypted data is then transmitted to
the remote apparatus by the IR transmitter in step 345.
[0076] It is feasible that the image capture, processing and
encryption steps are completed without any intervening steps of
storing data in RAM, that is to say processing is done
"on-the-fly", to greatly increase the speed of operation of the
apparatus. However, such processing would require more expensive
and more complex electronics.
[0077] Finally, if the data is received successfully by the remote
apparatus, the remote apparatus returns a `success` signal to the
imaging apparatus in step 360.
[0078] The processing means, in response, causes the optical
indicator to light up green to indicate to the user that the
procedure has been successful in step 360.
[0079] Repeated failure to transmit the data, for example after
five attempts, causes the optical indicator to light up red in step
355 and results in the user needing to restart the whole
procedure.
[0080] A simpler process than that described above involves the
imaging apparatus dictating which of the plurality of public
encryption keys to use. The selection can be made using a
pseudo-random number generator in the imaging apparatus. If each
public key has an index reference, the respective reference can be
included, obviously in non-encrypted form, with the encrypted data
to indicate to the remote apparatus which public key has been used
and, thus, which private key should be used for de-encryption. An
extension to this arrangement is that a new set of public keys is
down-loaded to the imaging apparatus, from the remote apparatus,
each time a successful transaction occurs. Other, further
encryption possibilities will be apparent to the skilled
person.
[0081] In alternative embodiments, security may be further improved
with the use of a personal identity card similar, for example, to a
bank card which holds personal identity information on a magnetic
strip. Alternatively, the personal identity card might be a
smart-card which holds data in electronic form. The card, smart
card, or an equivalent card or device, provides information in the
form of magnetic or electronic data held on the card, which
identifies a particular user.
[0082] This information can be read by the imaging apparatus, when
the card is inserted into a suitable slot provided therein, and
incorporated into the iris code along with, for example, other time
stamp and apparatus identity information, further similar
embodiments will become apparent to the skilled person.
[0083] FIG. 4a represents one possible configuration for
illumination having a plurality of different wavelength sources
412, 414 and 416. The diagram represents the view through the first
window 400 to the camera 405(the diagram does not take account of
the 45.degree. mirror). At the bottom of the view area inside the
body of the apparatus is provided an light-emitting diode (LED)
array comprising three LEDs, each producing NIR optical radiation
of a different wavelength band beyond about 700 nm. For example,
each band spreads over about 20 nm and each band is separated from
the next by about 200 nm. One of the LEDs may instead provide
visible light.
[0084] One reason for providing illumination sources having
different wavelengths stems from the observation that different
lighting conditions, to some extent, provide different images. This
is a result of the iris of an eye being a three-dimensional object
in which different wavelengths of light penetrate to, and reflect
from, different depths. For example, IR optical radiation
penetrates more deeply into the iris than visible light. Thus, a
broadband light source creates a far richer, more complex, image of
an iris than a narrow band light source can. An advantage of using
a narrow band light source is that a simpler image is produced
which can be captured using relatively cheap optics.
[0085] Another reason for providing illumination sources having
different wavelengths is that the degree of absorbtion of, say,
near infra-red light, by an iris is dependent on its colour.
Therefore to obtain an image having the required brightness,
different wavelength sources can be used for different colour
eyes.
[0086] The applicants have determined that different narrow band
light sources can be used to produce different iris images which as
a group form a family of images for one iris. Thus, one or more of
the images can be used to identify or validate a user. The choice
of which image to use can be determined by the remote apparatus.
This approach increases security by overcoming fraud which might be
possible otherwise by substituting a user with a photograph of an
eye.
[0087] Since a photograph is only two-dimensional, there would be
no, or at least a different, wavelength dependence in the images
produced, and the image would not vary regardless of which
wavelength of source was used.
[0088] Other embodiments in which separate images resulting from
different wavelengths of illumination are combined in different
ways will be apparent to the skilled person.
[0089] In practice, the array, and each of the LEDs individually,
is controlled by the processor (via suitable electrical circuitry
which is not shown). The processor controls when and which LEDs
light up to illuminate the eye, either in response to its own
controlling software or in response to signals received from the
remote equipment. The processor also determines when, and under
which lighting conditions, the image capturing process occurs. Said
lighting conditions depend on the image(s) required by the remote
equipment and, as has already been described, may be pulsed.
[0090] FIG. 4b is similar to FIG. 4a, except four identical LED
arrays are provided to produce a more even illumination of the
eye.
[0091] Instead of different wavelength sources, one or more
broadband sources may be used to illuminate the iris, with optical
filters used to isolate the required, different wavelength
bands.
[0092] The procedure relies on the remote apparatus being arranged
to receive, transmit and react in a complementary fashion to the
imaging apparatus. In one embodiment, the remote apparatus is a PC
programmed with suitable software and having a suitable transmitter
and receiver arrangement. Also, the PC is typically connected via a
data network to other remote apparatus, for example a database
server. In operation, once received by the PC, the encrypted iris
code data is directed across the network to the database server.
The database server decodes the data and accepts or rejects the
user as a valid or an invalid user.
[0093] FIG. 5a illustrates correct alignment of an eye 500 with
respect the rear window 520 of the apparatus. Correct alignment in
this example requires that the whole iris 530 of the eye 500 is in
the field of view of the window 520.
[0094] FIG. 5b, which uses the same reference numerals as FIG. 5a,
illustrates a potential problem with eye alignment with respect to
the rear window 520 of the apparatus. As shown, it is possible that
the pupil 510 of the eye 500 has a view through the window 520, but
at the same time a significant portion of the iris 530 is obscured
from view through the window. Whilst the user might have a
reasonable view through the apparatus of, for example, target
equipment, the CCD camera 135 would be unable to capture a full
iris image, which would prevent successful iris recognition.
[0095] FIG. 6 illustrates one possible way of encouraging a user to
align their eye correctly in relation to the rear window 620 of the
apparatus. The rear window 620 of the apparatus incorporates a
screen 625. The screen comprises a gelatin filter, for example a
Kodak.TM. Wratten filter No. 89B, which is transparent to
wavelengths greater than 700 nm and opaque to lower, visible
wavelengths. The screen has a hole 328 at or around its centre
which allows all wavelengths of light to pass through the screen.
The hole 328 is large enough to allow the pupil of the eye a view
(indicated by solid projection lines) through the screen. This view
is not interrupted by a 45.degree. mirror 645 which is
substantially transparent to visible wavelengths of optical
radiation, but reflecting to IR and NIR wavelengths.
[0096] The major portion of the screen 625 is opaque to visible
wavelengths of radiation, but transparent to IR and NIR
wavelengths. Thus, with suitable IR or NIR illumination (not
shown), an image of the iris 612 of the eye, visible through the
screen 625 and projected via the mirror 645 to a camera (not
shown), can be captured (as illustrated by the dashed projection
lines).
[0097] Other appropriate compositions of screen will become
apparent to the skilled person in view of the preceding
description. Indeed, any variations of screen providing a similar
advantage could be employed. For example, the major region may be
translucent rather than opaque to visible light. Alternatively, the
major region may simply be tinted with respect to the minor, pupil
aligning region to encourage the user to adopt the correct
alignment. Also, the screen may be reinforced with glass or
plastics materials, covering the hole to prevent, for example, dust
from entering the apparatus.
[0098] Clearly, an eye alignment technique employing a screen as
described above has potentially broader application than use in
conjunction with an apparatus according to the present invention.
Indeed, such a screen could be incorporated into any device or
apparatus requiring similar, correct eye alignment in relation to
the respective apparatus.
[0099] As an alternative to the hot mirror used in the above
embodiment, a cold-mirror may be used. The cold mirror has the same
position and orientation as the hot mirror but has a different
coating on its underside. The coating would be effective to reflect
most visible light whilst allowing the passage of near infra-red
light. The other alteration which is made in this alternative
embodiment is to swap the CCD camera and the LCD display about.
[0100] Obviously, also, the imaging apparatus according to the
invention has far wider application than database access user
validation. For example, the apparatus could be used to identify
the owner of a car to an engine immobiliser in the car: unless the
user is the owner, the car cannot be started. Many other uses of
the invention will become apparent to the skilled person on reading
the present description.
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