U.S. patent application number 10/067000 was filed with the patent office on 2002-09-19 for iris imaging telephone security module and method.
This patent application is currently assigned to IriScan, Inc.. Invention is credited to Cambier, James L., Musgrave, Clyde.
Application Number | 20020131623 10/067000 |
Document ID | / |
Family ID | 22737227 |
Filed Date | 2002-09-19 |
United States Patent
Application |
20020131623 |
Kind Code |
A1 |
Musgrave, Clyde ; et
al. |
September 19, 2002 |
Iris imaging telephone security module and method
Abstract
A compact, handheld imaging apparatus which can be used to
capture high-quality iris images for identification of a person.
The handheld iris imager is non-invasive and non-contacting and
comprises a camera, a cold mirror, a lens, and an illuminator. The
imager has sensors and indicators which assist a user in aligning
and focusing the device. The imager also automatically captures the
image when proper positioning is achieved. A template of the image
is then compared to a database of previously stored templates of
images to identify the person. The imager is integrated into a
telephone as a security module. The telephone cannot be unlocked
and used unless a user has been identified and authorized by the
imager.
Inventors: |
Musgrave, Clyde; (Frisco,
TX) ; Cambier, James L.; (Rome, NY) |
Correspondence
Address: |
Woodcock Washburn LLP
46th-Floor
One Liberty Place
Philadelphia
PA
19103
US
|
Assignee: |
IriScan, Inc.
|
Family ID: |
22737227 |
Appl. No.: |
10/067000 |
Filed: |
February 4, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10067000 |
Feb 4, 2002 |
|
|
|
09199369 |
Nov 25, 1998 |
|
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6377699 |
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Current U.S.
Class: |
382/117 ;
382/218 |
Current CPC
Class: |
A01K 11/006 20130101;
G06K 9/00 20130101; H04M 1/67 20130101; G07C 9/37 20200101; G06V
40/19 20220101; H04L 63/0861 20130101 |
Class at
Publication: |
382/117 ;
382/218 |
International
Class: |
G06K 009/00 |
Claims
What is claimed is:
1. A method of unlocking a telephone responsive to the
identification of a person, comprising the steps of: (a) storing
image information of the iris of at least one person's eye; (b)
illuminating an eye of an unidentified person having an iris; (c)
obtaining an image of said iris of said unidentified person; (d)
determining if said image is an image of sufficient quality for a
step (f) of comparing; (e) repeating steps (b) through (d) until
said image of sufficient quality is obtained; (f) extracting a
template from said obtained image; (g) comparing said template of
said obtained image with said stored image information to identify
said unidentified person; and (h) unlocking the telephone
responsive to a result of said step of comparing.
2. The method according to claim 1, further comprising the step of
activating an indicator if said image is of insufficient
quality.
3. The method according to claim 2, wherein said indicator is at
least one of an audible indicator and a visible indicator.
4. The method according to claim 1, further comprising the step of
activating an indicator if said image is of sufficient quality.
5. The method according to claim 4, wherein said indicator is at
least one an audible indicator and a visible indicator.
6. The method according to claim 1, further comprising the step of
activating an indicator responsive to said step of comparing.
7. The method according to claim 6, wherein said indicator is at
least one of an audible indicator and a visible indicator.
8. The method according to claim 1, wherein said step of
determining if said image is an image of sufficient quality
comprises the step of focus assessment processing said image.
9. The method according to claim 1, wherein said telephone is
unlocked if said step of comparing identifies said person.
10. The method according to claim 1, further comprising the step of
encrypting said template.
11. The method according to claim 1, further comprising the step of
transmitting said encrypted template to a central station.
12. The method according to claim 1, further comprising the step of
decrypting said encrypted template at said central station.
13. A method of authorizing use of a telephone comprising:
capturing an image of an iris of a user of a telephone; processing
the image of the iris of the user of the telephone to extract a
template; in response to authenticating the user of the telephone
by comparing the extracted template with at least one of a
plurality of templates of authorized telephone users, unlocking the
telephone.
14. The method according to claim 13, wherein capturing an image of
an iris of a user of a telephone comprises: positioning an iris
before a camera; illuminating the iris; and obtaining at least one
image of the iris.
15. The method of claim 13, wherein capturing an image of an iris
of a user of a telephone comprises creating a virtual image of the
iris with a concave cold mirror.
16. The method of claim 13, wherein the at least one of the
plurality of templates of authorized telephone users is stored in a
database.
17. The method of claim 14, wherein obtaining the at least one
image of the iris of the user of the telephone further comprises:
determining if the at least one image of the iris of the user of
the telephone is of sufficient quality to extract a template from
by determining if a focus score calculated for the obtained image
exceeds a predetermined value.
18. The method of claim 14, wherein obtaining the at least one
image of the iris of the user of the telephone further comprises:
in response to determining that a focus score calculated for the
obtained image is less than a predetermined value, activating an
indicator.
19. The method of claim 14, wherein obtaining the at least one
image of the iris further comprises: in response to determining
that a focus score calculated for the obtained image is less than a
predetermined value, a second image of the iris of the user is
automatically obtained.
20. The method of claim 13, wherein authenticating the user of the
telephone comprises: encrypting the template extracted from the
obtained iris image; transmitting the encrypted template to a
central station; decrypting the encrypted template at the central
station; comparing the decrypted template to at least one of a
plurality of pre-existing templates stored in at least one of a
memory and a database of authorized telephone users stored at the
central station; and determining that the decrypted template is
substantially identical to at least one of the plurality of
pre-existing templates stored at the central station.
21. The method of claim 13, wherein unlocking the telephone
comprises at least one of enabling placement of a call and sending
a signal to a telephone processor of the telephone, directing the
telephone processor to activate the telephone.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 09/199,369, filed Nov. 25, 1998, entitled "Iris Imaging
Telephone Security Module and Method".
FIELD OF THE INVENTION
[0002] The present invention relates in general to identification
of physical characteristics of a human being or other animal. More
particularly, the present invention relates to iris
recognition.
BACKGROUND OF THE INVENTION
[0003] Various technologies are used for uniquely identifying a
person in accordance with an examination of particular attributes
of either the person's interior or exterior eye. One of these
technologies involves the visual examination of the particular
attributes of the exterior of the iris of at least one of the
person's eyes. The iris of the human eye has random patterns of
striations, ciliary processes, crypts, rings, furrows and other
features which had been shown capable of generating highly unique
biometric templates for personal identification. In this regard,
reference is made to U.S. Pat. No. 4,641,349, "Iris Recognition
System", issued to Flom et al., and U.S. Pat. No. 5,291,560,
"Biometric Personal Identification System Based on Iris Analysis",
issued to Daugman. As made clear by these patents, the visible
texture of a person's iris can be used to distinguish one person
from another with great accuracy. Thus, iris recognition can be
used for such purposes as controlling access to a secure facility
or a bank automatic teller machine, for example. An iris
recognition system involves the use of an imager to video image the
iris of each person attempting access, and image processing means
for comparing this iris video image with a reference iris image on
file in a database.
[0004] Iris identification systems have been developed that are
capable of collecting images of the iris and processing them to
produce biometric templates. These templates may be used to
identify individual irises with extremely low error rates, on the
order of 1 in 10.sup.6. The systems capture the iris images using
stationary optical platforms that are often large, complex, and
expensive. The systems are difficult to use with minimal
cooperation of the subject being identified. As a result their
usefulness in many applications is limited.
[0005] The cellular telephone industry each year loses an estimated
$650 million to cellular fraud, principally due to cloning of
cellular telephones. Cloning involves re-programming a phone's
electronic serial number and telephone number to those stolen from
a legitimate subscriber. To counteract cloning, some service
providers have utilized personal authentication techniques such as
personal identification numbers (PIN) or voice verification to
verify that the authorized subscriber is using the phone. This is
unreliable because PIN number can be stolen or forgotten, and voice
verification messages may be recorded.
[0006] Although the art of human recognition systems is well
developed, there remain some problems inherent in this technology,
particularly the lack of an iris imager and security module
suitable for integration into a cellular telephone, and the lack of
a method for using biometric information for enabling access to the
cellular network. Therefore, a need exists for a recognition system
that overcomes the drawbacks of the prior art.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to a telephone security
module comprising: iris acquisition means having a front surface
for obtaining an image of an iris of an eye; a lens having a image
plane disposed in front of the front surface of the iris
acquisition means; a mirror disposed on a side of the lens opposite
the iris acquisition means; an illuminator disposed along a side of
the mirror; a memory for storing an iris image obtained by the iris
acquisition means; a processor for extracting a template from the
stored iris image; and a communications interface for transmitting
the template to a central station.
[0008] According to one aspect of the invention, the iris
acquisition means comprises a camera, and the mirror is a cold
mirror. The camera is sensitive to light having a wavelength in a
range between about 400 nm and about 1100 nm. The mirror reflects
light having a wavelength in a range between about 400 nm and about
700 nm and passes light having a wavelength greater than about 700
nm.
[0009] According to another aspect of the present invention, the
illuminator emits light having a wavelength in a range between
about 680 nm and about 900 nm towards the iris of the eye being
imaged, and the eye is out of contact with the iris imaging
apparatus.
[0010] According to another aspect of the present invention, the
module further comprises at least a visible indicator or an audible
indicator to indicate when the image of the iris has been obtained.
According to another aspect of the present invention, the module
further comprises a focus assessment processor coupled to the
visible indicator and/or the audible indicator.
[0011] According to another aspect of the present invention, the
processor unlocks a telephone responsive to a signal received from
the central station.
[0012] In a further embodiment within the scope of the present
invention, a method of unlocking a telephone responsive to the
identification of a person comprises the steps of: (a) storing
image information of the iris of at least one person's eye; (b)
illuminating an eye of an unidentified person having an iris; (c)
obtaining an image of the iris of the unidentified person; (d)
determining if the image is an image of sufficient quality for a
step (f) of comparing; (e) repeating steps (b) through (d) until
the image of sufficient quality is obtained; (f) comparing a
template of the obtained image with the stored image information to
identify the unidentified person; and (g) unlocking the telephone
responsive to a result of the step of comparing. The stored image
information used for identification can be a code or template
extracted from the image, and the comparison can be performed at a
central database maintained by a telephone service provider.
[0013] According to one aspect of the present invention, the method
further comprises the step of activating an indicator if the image
is of insufficient quality. The indicator is an audible
indicator.
[0014] According to another aspect of the present invention, the
method further comprises the step of activating an indicator if the
image is of sufficient quality. The indicator is a visible
indicator.
[0015] According to another aspect of the present invention, the
method further comprises the step of activating an indicator
responsive to the step of comparing. The indicator is a visible
indicator.
[0016] In accordance with a further aspect of the present
invention, the step of determining if the image is an image of
sufficient quality comprises the step of focus assessment
processing the image.
[0017] According to another aspect of the present invention, the
telephone is unlocked if the step of comparing identifies the
person.
[0018] In a further embodiment within the scope of the present
invention, a system of identification of a person for unlocking a
telephone comprises a telephone security module, a second memory
for storing at least one template of at least one image of an iris
of at least one person's eye; and a second processor for comparing
the template of the stored iris image with the at least one stored
template of the second memory to identify the person, and for
unlocking the telephone responsive to the result of the
comparison.
[0019] In accordance with a further aspect of the present
invention, the second memory and second processor are housed in a
central station remote from the telephone security module.
[0020] In accordance with a further aspect of the present
invention, the second processor unlocks the telephone when the
template of the stored iris image substantially matches the at
least one stored template of the second memory.
[0021] In a further embodiment within the scope of the present
invention, a telephone security module comprises: iris acquisition
means having a front surface for obtaining an image of an iris of
an eye; a lens having a image plane disposed in front of the front
surface of the iris acquisition means; a mirror disposed on a side
of the lens opposite the iris acquisition means; an illuminator
disposed along a side of the mirror; a first memory for storing at
least one template of at least one image of an iris of at least one
person's eye; a second memory for storing an iris image obtained by
the iris acquisition means; a processor for extracting a template
from the stored iris image; and a comparator for comparing the
template from stored iris image with the at least one template to
identify the person.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The foregoing and other aspects of the present invention
will become apparent from the following detailed description of the
invention when considered in conjunction with the accompanying
drawings. For the purpose of illustrating the invention, there is
shown in the drawings an embodiment that is presently preferred, it
being understood, however, that the invention is not limited to the
specific methods and instrumentalities disclosed. In the
drawings:
[0023] FIG. 1 is a schematic diagram of an exemplary iris imager in
accordance with the present invention;
[0024] FIG. 2A is a schematic diagram of the imager of FIG. 1 shown
in greater detail;
[0025] FIG. 2B is a schematic diagram of another exemplary imager
in accordance with the present invention;
[0026] FIG. 3 is a simplified flowchart of a method of operation in
accordance with the present invention;
[0027] FIG. 4 is a schematic diagram of an exemplary iris image
recognition system in accordance with the present invention;
[0028] FIG. 5 is a schematic diagram of an exemplary iris imager
having visual and aural indicators in accordance with the present
invention;
[0029] FIG. 6 is a more detailed flow chart of a method of
operation in accordance with the present invention;
[0030] FIG. 7 is a schematic diagram of an exemplary iris image
recognition system having a focus assessment processor in
accordance with the present invention;
[0031] FIG. 8 is a schematic diagram of an exemplary iris imager
incorporated into a telephone in accordance with the present
invention;
[0032] FIG. 9 is an isometric view of an exemplary
telecommunications iris imager and telephone in accordance with the
present invention; and
[0033] FIG. 10 is a flow diagram of an exemplary method of
operation of a telecommunications iris imager in accordance with
the present invention.
DESCRIPTION OF EXEMPLARY EMBODIMENTS AND BEST MODE
[0034] The present invention is directed to a compact, handheld
imaging apparatus and method which can be used to capture
high-quality iris images. Preferably, the imager has sensors and
indicators which assist the human operator in aligning and focusing
the device. The imager also automatically captures the image when
proper positioning is achieved. Because it is small and compact, it
is practical for integration into a cellular telephone where it is
used to authenticate telephone subscribers and eliminate cellular
telephone fraud. Throughout the following detailed description
similar reference numbers refer to similar elements in the figures
of the drawings.
[0035] FIG. 1 illustrates a preferred embodiment of the handheld
imager 100 in accordance with the present invention. The exemplary
handheld, non-invasive, non-contacting iris imager comprises iris
acquisition means 105, an imaging lens 110, a mirror 120, an
optional diopter correction lens 125, and an illuminator 130. The
imager 100 is preferably powered by a standard DC supply provided
by a cellular telephone.
[0036] The iris acquisition means 105 is preferably a conventional
solid state video camera, such as a charged coupled device (CCD) or
complementary metal oxide semiconductor (CMOS) device. A preferred
camera is a 1/3 inch format, monochrome CCD board camera, such as
Computar Model EM200. Preferably, the video camera 105 is sensitive
to light of wavelengths in the range of about 400 nanometers to
about 1100 nanometers, and is positioned so that its front surface
coincides with the image plane of the lens 110 in front of it. In
the preferred embodiment, the object plane of the lens is
approximately 89 mm in front of the lens 110. More preferably, the
lens 110 is an optical lens with approximately 14.2 mm focal
length.
[0037] The mirror 120, preferably a concave cold mirror having a
radius of curvature preferably about 276 mm, is disposed on the
side of the lens 110 opposite the video camera 105 and creates a
magnified virtual image of the iris behind the mirror 120. In the
preferred embodiment, the mirror 120 reflects visible light with
wavelengths in the range of about 400 to about 700 nanometers, and
passes light having longer wavelengths, such as those in the range
of about 700 to about 900 nanometers.
[0038] The illuminator 130 is positioned just outside the edge of
the cold mirror 120 and is used to illuminate the iris of the
subject being identified. The preferred illuminator 130 emits light
having wavelengths of about 680 to about 900 nanometers.
Preferably, the illuminator 130 is a miniature quartz halogen or
krypton gas bulb operating at approximately 1 watt.
[0039] The imager acquires images of an iris with sufficient
clarity, focus, and size for use with conventional image processing
and comparison routines, preferably in less than about 3 seconds. A
preferred image processing and comparison routine is described in
U.S. Pat. No. 5,291,560, "Biometric Personal Identification System
Based on Iris Analysis", issued to Daugman, and commonly assigned
with the present invention to Iridian Technologies Inc., and
incorporated herein by reference. However, any processing and
comparison technique can be used with the image that is acquired at
the imager, such as the image pixel correlation technique described
in U.S. Pat. No. 5,572,596, "Automated, Non-Invasive Iris
Recognition System and Method", issued to Wildes et al. and the
techniques described in U.S. Pat. No. 4,641,349, "Iris Recognition
System", issued to Flom et al., both of which are incorporated
herein by reference.
[0040] FIG. 2A shows the apparatus of FIG. 1 in greater detail. The
lens 110 gives a high resolution image of the eye 150 of the user,
who is positioned in front of the lens 110, so that extreme
proximity between the eye 150 and the imager 100 is not required
(i.e., no contact is needed between the subject and the imager
100).
[0041] The handheld iris imager comprises a solid-state image
capture device and an optical system which forms an image 109 of
the iris on the image capture device at the image plane of the
video camera 105 and at the same time produces a virtual image 115
of the iris which the user can use to position and focus the iris
image. As a result, the user can, using the same eye being imaged,
see a reflected image of the iris which can be used to position the
handheld imager 100 so that a good iris image (i.e., an image that
can be processed and compared to those stored in a database) can be
obtained.
[0042] FIG. 2A also shows an optional dioptric correction lens 125
positioned between the eye 150 and the cold mirror 120. The
dioptric correction lens 125 is an adjustable optical element which
corrects for the close-range focusing ability of the individual
eye, which varies from subject to subject. When the lens 125 is
properly adjusted, the magnified, reflected virtual image 115 of
the subject's eye appears in sharp focus to the subject at the same
eye-to-mirror distance at which the subject's eye is sharply
focused on the front surface of the camera. This simplifies use of
the imager, because the subject simply positions the image so that
the virtual image 115 of the iris appears sharply focused.
[0043] A preferred embodiment of the dioptric correction mechanism
has no correction lens 125 and instead has a mechanical means (not
shown) for adjusting the position of the cold mirror 120 relative
to the camera lens 110. This allows the user to vary the object
distance of the cold mirror 120, thus changing the eye-to-lens
distance at which the virtual image 115 of the iris is sharply
focused.
[0044] The ability to set the dioptric correction mechanism to
accommodate a particular user has a great utility if the imager is
used by only one person most of the time. Once the correction is
set, the user can easily position the device to obtain a sharply
focused reflected image. This automatically produces a sharply
focused image from the camera and substantially immediate
acceptance of the image by the focus assessment processor described
below. Image capture time is thereby reduced and overall
convenience and utility is enhanced.
[0045] An eye 150 is positioned in front of the imager 100 (e.g.,
about 3.5 inches in front), as shown in FIG. 2A, and the
illuminator 130 is turned on. This, in turn, illuminates the eye
150 and the iris therein. Preferably, the light having wavelengths
of about 400 to about 700 nanometers is reflected by the cold
mirror 120, thereby forming a magnified virtual image 115 behind
the mirror 120 which the user can see through the eye being imaged.
The radius of curvature of the mirror is selected so that the
magnified image 115 of the eye substantially fills the user's
entire field of view. Hence, when the imager 100 is positioned so
that the entire eye 150 is visible, it is virtually assured that
the eye 150 will be substantially centered in the object plane 140
of the camera 105. Under these conditions, the light having
wavelengths of about 700 to about 900 nanometers is passed by the
mirror 120 and forms an approximately centered image 109 of the eye
150 at the image plane 107 of the camera 105. The image is then
captured and processed, as described below.
[0046] Although a cold mirror (one which reflects shorter
wavelengths and passes longer wavelengths) is described herein, it
is understood that a hot mirror (one which reflects longer
wavelengths and passes shorter wavelengths) could also be used in
accordance with the present invention. Such a configuration is
shown in an imager 101 in FIG. 2B. The eye 150 is illuminated by an
illuminator 131 emitting light having wavelengths in the range of
about 680 to 900 nanometers. This light is reflected by the eye 150
and the light having wavelengths in the range of about 700 to 900
nanometers is reflected by the hot mirror 121 to be focused by the
lens 111 onto the front surface of the camera 106. Light reflected
from the eye 150 having shorter (visible) wavelengths in the range
of about 400 to 700 nanometers passes through the hot mirror 121
and strikes a concave broadband mirror 122 which reflects light
having wavelength from about 400 to 900 nanometers. This light
forms a virtual image 115 of the eye 150 behind the concave mirror
122 that the user can see and use to align and focus the device, as
described below.
[0047] The imager 100 of FIGS. 1 and 2A, as well as the imager of
FIG. 2B, is used in a system to identify the iris image that has
been captured. As shown in FIG. 3, the eye is illuminated at step
160, and an acceptable or suitable image of the iris is obtained at
step 165. The image is processed to extract an iris template or
code at step 170, the template or code is encrypted (optional) and
transmitted to the cellular provider (such as a central station;
e.g., a Mobile Telephone Switching Office) at step 175, and the
template or code is decrypted (if necessary) and compared to
pre-existing templates or codes of authorized subscribers stored in
a memory or database for identification and authorization of the
user at step 180. If the user is authorized, the cellular provider
enables the call placement at step 185. The cellular provider can
either enable the call at the central station or send a signal to
the telephone processor directing it to unlock the telephone.
[0048] FIG. 4 is a schematic diagram of an exemplary iris image
recognition system in accordance with the present invention. The
imager 100 is coupled to a microprocessor 210 that performs the
processing and encryption. The microprocessor 210 resides in a
cellular telephone 200.
[0049] The microprocessor 210 is coupled to the imager 100 via
conventional cables and/or printed circuit boards (PCBs) that are
incorporated into the telephone 200. Other conventional means for
coupling the imager 100 and the microprocessor 210 can be employed.
The microprocessor 210 controls the imager 100 and runs software
held in read only memory (ROM) 205. The processor 210 is connected
via a bus 207 to the ROM 205, a random access memory (RAM) 232,
another memory such as an erasable programmable ROM (EPROM) 230,
and an input/output (I/O) controller 225. The RAM 232 is large
enough to hold at least one captured image of an iris. The I/O
controller 225 is connected to the appropriate circuitry and
drivers (not shown) for issuing commands to control the imager
100.
[0050] The imager 100 preferably uses a digital camera and
transmits digital images directly to the processing unit 210.
"On/off" data is transmitted from the imager 100 to the processor
210 to initiate the image acquisition function. A digital image
could be provided if a digital camera is used.
[0051] The image processing consists of a number of image
processing steps (such as those described in U.S. Pat. No.
5,291,560 and U.S. Pat. No. 5,572,596, which are herein
incorporated by reference) which lead to extraction of a unique and
highly specific digital biometric template that can be used to
identify the individual based on intensity patterns within the
iris. The biometric template is transmitted to the cellular
provider where it is compared against other templates stored in a
memory or database. The database stores selected data representing
images of the iris of a plurality of subjects. A match of the
biometric template with a template stored in the database
identifies the subject whose iris is being imaged.
[0052] Although an image of the eye is reflected back to the
subject in mirror 120, this may not provide the desired feedback to
the user to enable the user to properly position the imager so that
a suitable iris image is obtained. For example, a user may be a
novice in using and positioning the imager 100 with respect to the
eye 150, or the user may be attempting to image the eye of another
subject with the imager. Thus, preferably, the imager 100 comprises
a passive feedback mechanism to guide the user in positioning the
eye 150 to an optimum location to allow acquisition of a suitable
image.
[0053] The passive feedback mechanism is an indicator or
combination of indicators that provides, on a near real-time basis,
an indication to the user that an adequate iris image has or has
not been obtained. FIG. 5 is a schematic diagram of an exemplary
iris image recognition system that includes position indicators in
accordance with the present invention. Preferably, the indicator is
visible and/or audible, such as, for example, an indicator lamp 305
(e.g., a light emitting diode (LED)) that lights when an acceptable
image has been captured (i.e., "image acquired"), and a aural
indicator via a speaker 310, such as a beep or other tone, that
sounds periodically until an acceptable image has been captured
(i.e., "imaging in progress").
[0054] Additional indicators 306, 307 can be also be used, either
alone or in combination, for such indications as "subject
identified--accept" and "subject not identified--reject". These
indications would be activated pursuant to the results of the
processing and comparison performed at the database server at the
cellular provider, as described above with respect to FIG. 3.
Alternatively, other display devices, such as liquid crystal
displays used for other purposes within the telephone, could be
used as indicators.
[0055] The imager 100 also preferably has an on/off switch (not
shown), such as a pushbutton, for powering up the imager and
initiating the image acquisition process. Power for the imager 100
is preferably supplied by a battery. The imager 100 receives and
acts on instructions from the processor 210 to perform functions
such as lighting or turning off the indicator lamp(s) 305,
providing the audible signals via the speaker 310, and lighting the
`accept` and `reject` indicators.
[0056] FIG. 6 is a more detailed flow chart of a method of
operation in accordance with the present invention. The eye is
illuminated at step 350 and an image of the iris is obtained at
step 355. At step 360, it is determined if the image is suitable
for use with the image processing and comparison routines. If the
image is suitable, the image is passed to the processor for further
processing, at step 370, and transmission to the cellular provider.
A comparison of the template to the templates stored in a database
at the cellular provider is performed at step 373. If the
comparison provides a positive match, then authorization is granted
at step 376 for the user to use the phone. If the comparison does
not provide a positive match, then authorization is not granted for
the user to use the phone.
[0057] If the image is not suitable at step 360, then at step 380,
the indicator(s) is activated (e.g., a beep sound is issued), and
processing continues at step 355 (i.e., another image is
obtained).
[0058] Because the eye's own focusing system automatically adjusts
to bring the virtual image 115 into sharp focus to the user, it
cannot be relied upon to always accurately focus the eye image on
the camera 105. For this purpose, a focus assessment system is used
in one embodiment, as shown in FIG. 7. Digital video image
information from the imaging device 100 is stored in a frame buffer
memory 410, such as a RAM similar to RAM 232 described above with
respect to FIG. 4, and capable of storing one complete frame of
digitized video information. A focus assessment processor 420
accesses the digitized image information and applies certain
measurement algorithms which are disclosed in a co-pending
application entitled "Video-Rate Focus Assessment", filed
concurrently with this application (Attorney Docket No. ICAN-0067),
and incorporated herein by reference. The output of the focus
assessment is used to control an indicator, such as the audible
indicator 310. As long as the focus assessment processor 420
determines that the captured image is not acceptable for further
processing and comparison, the audible indicator 310 is directed to
emit periodic sounds to alert the user. Images are repeatedly
acquired and assessed until an acceptable one is received. After an
acceptable iris image has been received, the audible indicator 310
is turned off and the final image is retained for further
processing and comparison, for example, by the microprocessor 210,
as described above.
[0059] Any known technique for image focusing can be used with the
imager of the present invention, such as those described in U.S.
Pat. No. 4,876,608, entitled "Focus and Signal to Noise Measurement
Routines in Input Scanners", issued to Eaton, U.S. Pat. No.
5,151,583, entitled "Focus Adjustment Device Having Restricting
Means for Restricting a Selecting Action According to the Degree of
Nearness of a Distance Measurement", issued to Tokunaga et al., and
U.S. Pat. No. 5,404,163, entitled "In-Focus Detection Method and
Method and Apparatus Using the Same for Non Contact Displacement
Measurement", issued to Kubo. The preferred system and method for
focus assessment is described below.
[0060] A focus score is computed for each video frame (i.e., each
captured image). If the focus score exceeds a predetermined value,
then it is determined that the image is focused enough for further
processing and comparison. If the focus score does not exceed the
predetermined value, then it is determined that the image is not
focused enough for further processing, and an indicator (such as
indicator 310, described with respect to FIG. 5) is activated and a
further image is captured. Alternatively, a sequence of image
frames can be obtained that cycle through a range of focus
distances strobed at the video frame-rate, and the focus score
computed for each frame can enable the selection of the best
focused frame within the sequence of frames. For example, by
obtaining image frames at each of several different lens settings
and then fitting a spline curve to their respective focus scores
one can predict the lens position that would deliver substantially
the sharpest focus, by setting the derivative of the parameterized
spline curve to zero and then solving the equation for
position.
[0061] Specific implementation features of the preferred focus
assessment system and method which enable its real-time operation,
include (1) the computation of quantities in the 2D Fourier domain,
without needing to compute an actual 2D Fourier Transform of an
image (this avoids the need for approximately 2.25 million
floating-point operations required for an FFT (Fast Fourier
Transform) on a 500.times.500 pixel image, as the computational
complexity of an FFT on n.times.n data is O(n.sup.2log.sub.2n));
(2) only 6,400 integer multiplications (squarings) are performed,
which in turn can be eliminated altogether by using small look-up
tables; (3) no floating-point operations are required; (4)
computation of focus scores is based upon simple algebraic
combinations of pixel values within local closed neighborhoods,
repeated across regions of the image; and (5) these operations not
only allow the algorithm to execute in real-time, but it also
enables a straightforward implementation in simple, low-cost,
hardware devices that could be embedded within a digital camera or
frame grabber.
[0062] Preferably, the focus assessment processor 420 is fast
enough to determine a focus score for each frame in a video image
stream in less than the time it takes to acquire a new frame (e.g.,
approximately 25 ms). The frame-by-frame focus scores can be used
to control a moving lens element for rapid and accurate focus
control, or alternatively, to select which of several frames in a
video stream is the one in best focus. The rapid selection of
well-focused video frames for further processing, such as image
analysis and pattern recognition, is important in real-time
computer vision because it prevents wasting processing time on
poorly-focused images.
[0063] The preferred focus assessment processor measures the focus
quality of video images at standard rates of 25 (PAL) or 30 (NTSC)
frames per second.
[0064] It is contemplated that the focus assessment processor 420
can be implemented in a general purpose personal computer (PC) or
by a dedicated, low cost processor which is small enough to be
incorporated into the camera electronics.
[0065] The processing of a video frame results in the return of an
integer value (on a scale between 0 and 100) reflecting the quality
of focus; the larger the value of the integer, the better the
focus. A value of 0 indicates a completely defocused image whereas
the value of 100 indicates maximum focus quality. A predetermined
threshold is used to determine whether an image is sufficiently
focused or whether another image needs to be retrieved. For
example, values greater than about 40 can indicate sufficient
quality of focus to warrant further image processing, while values
less than about 40 cause a new image frame to be grabbed, and
optional feedback provided to the focusing mechanism, if one
exists, or to the subject controlling the camera position (via the
indicator 310, for example).
[0066] Optical defocus is a phenomenon of the 2D Fourier domain. An
image represented as a 2D function of the real plane, I(x,y), has a
2D Fourier Transform F(.mu., v) defined as shown in equation 1. 1 F
( , v ) = 1 ( 2 .PI. ) 2 x y I ( x , y ) e i ( x + vy ) x y ( 1
)
[0067] In the image domain, defocus is preferably represented as
convolution by the 2D point-spread function of the defocused
optics. This in turn may be modeled as a Gaussian whose space
constant is proportional to the degree of defocus. Thus, for
perfectly focused optics, the optical point-spread function shrinks
almost to a delta function, and convolution with a delta function
causes no change to the image. Progressively defocused optics
equates to convolving with a wider and wider point-spread function,
which averages together whole neighborhoods of pixels by such a
weighting function, thereby producing an increasingly blurred
image.
[0068] If the convolving optical point-spread function causing
defocus is modeled as a Gaussian whose width represents the degree
of defocus, then defocus is equivalent to multiplying the 2D
Fourier Transform of a perfectly focused image with the 2D Fourier
Transform of the "defocusing" (convolving) Gaussian. This latter
quantity is itself just another 2D Gaussian but in the Fourier
domain, and its space constant (.sigma.) there is the reciprocal of
that of the image-domain convolving Gaussian that represented the
optical point-spread function. The preferred focus assessment
processor uses (1) the duality of convolution and multiplication in
the two domains; (2) the fact that a Gaussian has a Fourier
Transform which is itself a Gaussian, but with the reciprocal width
because of (3) the Similarity Theorem. Thus, the 2D Fourier
Transform D.sub..sigma.(.mu., v) of an image defocused to degree
.sigma. is related to F(.mu., v), the 2D Fourier Transform of the
corresponding in-focus image, as given by equation 2. 2 D ( , v ) =
e - ( 2 + v 2 2 ) F ( , v ) ( 2 )
[0069] From the above equation, the effect of defocus is to
attenuate primarily the highest frequencies in the image, and that
lower frequency components are virtually unaffected by defocus
since the exponential term approaches unity as the frequencies
(.mu., v) become small. For simplicity, the present description has
assumed isotropic optics and isotropic blur, and the optical
point-spread function has been described as a Gaussian. However,
the analysis can readily be generalized to non-Gaussian and to
anisotropic optical point-spread functions.
[0070] Thus, an effective way to estimate the quality of focus of
an image is to measure its total amount of energy in the 2D Fourier
domain at high spatial frequencies, since these are the most
attenuated by defocus. One may also perform a kind of "contrast
normalization" to make such a spectrally-based focus measure
independent of image content, by comparing the ratio of energy in
the highest frequency bands to that in slightly lower frequency
bands. Such spectrally-based energy measurements are facilitated by
exploiting Lord Rayleigh's theorem for conserved total power in the
two domains, shown in equation 3.
.intg..sub.-.infin..sup.+.infin..intg..sub.-.infin..sup.+.infin..vertline.-
/(x,y).vertline..sup.2dxdy=.intg..sub.-.infin..sup.+.infin..intg..sub.-.in-
fin..sup.+.infin..vertline.F(.mu., v).vertline..sup.2d.mu.dv
(3)
[0071] Thus, high-pass filtering or band-pass filtering an image at
a ring of high spatial frequency (using only convolution in the 2D
image domain) and measuring the residual energy, is equivalent to
making the corresponding energy measurement in the high frequency
bands of the 2D Fourier domain. The appropriate measurements in the
2D Fourier domain to assess focus can be performed without
computing a time-consuming 2D Fourier Transform. Indeed, the
measurements can be performed without even a single floating-point
operation, and even without any multiplications if appropriate
convolution kernels and look-up tables are used.
[0072] A real-time procedure for focus assessment based on these
theoretical principles is used in the focus assessment processor
420. It executes much faster than the video frame-rate, and so
real-time focus assessments can be made on a frame-by-frame basis.
These can be used either to control the position of a focusing lens
element, or alternatively as a type of autofocus system in which
frames are grabbed at a variety of focal depths in order to select
only the best one for processing, or to prevent time being wasted
on processing image frames which are assessed to be in poor
focus.
[0073] The 2D spectral measurements described above can be
implemented by convolving an image with the following convolution
kernel, in which pixel values within a predetermined region, such
as, for example, an (8.times.8) neighborhood, are added together
with the weights indicated in each of the cells:
1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 +3 +3 +3 +3
-1 -1 -1 -1 +3 +3 +3 +3 -1 -1 -1 -1 +3 +3 +3 +3 -1 -1 -1 -1 +3 +3
+3 +3 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
[0074] It should be noted that no pixel-by-pixel multiplications
are needed in order to impose these weights. Rather, the pixels in
the central region are added together, such as the (4.times.4)
square, that sum is tripled, and then all pixel values in the outer
two pairs of rows and columns are subtracted from the tripled sum.
The result is squared and added to an accumulator, thus
implementing the left-hand side of equation (3) above for this
local region of the image. The complete (8.times.8) convolution
kernel is then moved to a new position in the image, along a
sampling grid that selects every 4th row and every 4th column, and
the operation is repeated. Thus, to assess the quality of focus
within the central (320.times.320) region of an image, this set of
64 pixel summations followed by a squaring operation is repeated a
total of (320/4).sup.2=6,400 times.
[0075] In the 2D Fourier domain, the spectral consequences of this
operation can be appreciated by examining the 2D Fourier Transform
of the convolution kernel above. The kernel is equivalent to the
superposition of two centered square box functions, one of size
(8.times.8) and amplitude-1, and the other of size (4.times.4) and
amplitude +4 (for the central region in which they overlap, the two
therefore sum to +3). The 2D Fourier Transform of each of these
square functions is a 2D "sinc" function, whose size parameters
differ by a factor of two in each of the dimensions and whose
amplitudes are equal but opposite, because the two component boxes
have equal but opposite volumes. Thus, the overall kernel has a 2D
Fourier Transform K(.mu., v) which is the difference of two
differently-sized 2D sinc functions, as given by equation 4. 3 K (
, v ) = sin ( ) sin ( v ) .PI. 2 v - sin ( 2 ) sin ( 2 v ) 4 .PI. 2
v ( 4 )
[0076] This is a high-pass (or ultimately a band-pass) filter,
selecting only a high range of spatial frequencies in all
orientations. Towards its center, corresponding to very low spatial
frequencies, its value approaches zero (as can also be inferred
from the fact that the sum of all pixel weights in the convolution
kernel shown above is zero). Thus, low frequencies play little or
no role in computing a focus score, and only relatively high
frequencies contribute significantly to the computation of a focus
score. Equation (3) shows that summing the squares of all the local
convolution sums across the image is equivalent to summing the
total amount of high frequency energy in the 2D Fourier Transform
of the image. The action of the convolution kernel is to impose the
above power spectral weighting function so that primarily high
frequency energy is measured.
[0077] Finally, the summated 2D spectral energy is passed through a
compressive nonlinearity of the form .function.(x)=100
x.sup.2/(x.sup.2+c.sup.2) in order to generate a normalized focus
score in the range of 0 to 100 for any image.
[0078] The focus assessment technique is applied immediately after
each image frame is digitized and stored in the frame buffer memory
410 in order to assess whether the focus quality is sufficient to
warrant any further processing. If the calculated focus quality
value of the captured image is greater than or equal to a
predetermined value, the image is passed to applicable programs for
further processing, for example for extraction of a biometric
template. The focus assessment technique can be used to compare the
relative focus of an entire series of images in order to select the
one most in-focus (i.e. having the highest focus assessment score),
as well as to measure a single image.
[0079] The focus assessment technique can be used to provide a
feedback indication to a system user who controls the position of
the imager relative to the object being imaged. This can be
accomplished by activating an indicator which would continue, while
successive images are captured and their focus assessed, until the
focus assessment score exceeds a predetermined value. At this
point, the indicator is deactivated and the last image captured is
transferred to the image processor 210 where it is processed to
extract the biometric template.
[0080] The application of the focus assessment technique in
combination with the feedback indicator helps resolve the
man-machine interface problems associated with the use of digital
imaging devices on the eye. Individuals using the system are
provided positive, objective indicators and feedback as to the
quality of image focus. The focus assessment processor can also be
used in any situation where it is required to determine the quality
of focus of video images at industry standard frame rates (NTSC and
PAL).
[0081] Thus, the image is obtained at the imager and transmitted to
an analog to digital converter 405. The digitized video information
is then stored in a frame buffer memory 410. The focus assessment
processor 420 isolates the central 320.times.320 region of the
image. 8.times.8 pixel blocks (each pixel is in only one block) are
then processed by first summing pixels in the central 4.times.4
region, tripling that sum, and then subtracting from this value all
the pixel values in the outer two pairs of rows and columns. This
result is then squared. This process is performed on each 8.times.8
block, and the results are summed. After the entire image has been
processed, the summed result is compressed nonlinearly to generate
a focus score between 0 and 100. This score is then compared to a
predetermined number for determining if the indicator 310 should be
activated.
[0082] The focus assessment is preferably performed by the
microprocessor 210, or it can be a separate processor element
within the telephone.
[0083] It is contemplated that in addition to the focus assessment
processor, an auto-focus lens system could be used in the present
invention. The results of the focus assessment control the lens
system, thereby automatically adjusting focus to produce an optimal
image. This would place less of a premium on the accuracy with
which the user positions the eye, and would be helpful if the user
could not see or hear the indicators described above.
[0084] The iris imager of the present invention can be used as a
security module for electronic devices such as a telephone. FIG. 8
is a schematic diagram of an exemplary iris imager incorporated
into a telephone in accordance with the present invention. The
imager 700 comprises the camera 105, lens 110, mirror 120, and
illuminator 130, as described above with respect to FIG. 1. The
imager 700 also comprises visible indicators 555, 556, 557, which
are similar to indicators 305, 306, 307, respectively, described
above with respect to FIG. 5. An audible indicator 560, similar to
indicator 310, is also disposed within the imager 700. The imager
700 further comprises electronics and circuitry 500 for processing
and comparing the obtained image. The electronics and circuitry 500
comprises a microprocessor 510 (similar to microprocessor 210) that
controls the imager 700 along with an I/O controller 525 and runs
software held in a ROM 505. The processor 510 is connected to the
ROM 505, a RAM 532 that is capable of storing at least one captured
image or an iris, another memory 530, such as an EPROM, for storing
a plurality of biometric templates or iris images that are to be
compared with the captured iris image. The electronics and
circuitry 500 is also connected to the camera 105, the illuminator
130, and the indicators 555, 556, 557, 560 for controlling these
elements of the imager 700. The processor can also comprise a focus
assessment processor, similar to the focus assessment processor
420.
[0085] It should be noted that in the embodiment of FIG. 8, the
database memory 530 of templates is stored within the imager 700
and not at a central station (as described, for example, with
respect to FIG. 4), as is the processor 510 used in the comparison.
In the embodiment of FIG. 8, the comparison of the captured image
template with the stored templates takes place locally within the
telephone, and no data is sent to the central station for
comparison or authentication.
[0086] The imager 700 is coupled to telephone electronics 570 for
transmitting encrypted or unencrypted data to another telephone or
system via an antenna. The telephone electronics 570 is essentially
a telephone and is preferably a conventional cell phone having
telephone electronics and is connected to a transmission antenna.
Preferably, a conventional voltage regulator (not shown) provides
the appropriate operating voltage to the imager 700 from the power
supply (e.g., a battery) of the phone.
[0087] Preferably, the imager 700 of the present invention is
incorporated into a handset of a telephone 575, as shown in FIG. 9.
The present invention can be incorporated into a conventional
digital cell phone, as shown in FIG. 9, such as those manufactured
by Qualcomm.
[0088] FIG. 10 is a flow diagram of an exemplary method of
operation of a telecommunications iris imager in accordance with
the present invention. A user desiring to make a telephone call
first unlocks the telephone by having his iris identified by the
imager residing within the phone. The eye, and thus the iris, is
illuminated at step 605. An image is obtained of the iris at step
610. At step 615, it is determined if the image is suitable for
further processing and comparison, as described above. If the image
is not suitable, the appropriate indicators are activated at step
620, and processing returns to step 610 with the capture of another
iris image.
[0089] If the captured image is suitable for further processing,
the image is processed at step 630 (an indicator can be activated
to alert the user that a suitable image has been captured) and is
compared to the stored images residing in a database, for example,
in a memory, at step 635. If there is no match between the captured
image and the stored images, at step 640, the appropriate
indicators are activated at step 645, and the imaging routine
exits. In this manner, the telephone remains locked, and cannot be
used because it is determined that the user is unauthorized.
[0090] If there is a match between the captured image and the
stored images, at step 640, the phone is unlocked (and an indicator
can be activated) at step 650, and the user is then able to use the
phone to place a call, for example. The phone can be returned to
its locked, secure state either upon being powered down or upon
completion of the phone call.
[0091] Although illustrated and described herein with reference to
certain specific embodiments, it will be understood by those
skilled in the art that the invention is not limited to the
embodiments specifically disclosed herein. Those skilled in the art
also will appreciate that many other variations of the specific
embodiments described herein are intended to be within the scope of
the invention as defined by the following claims.
* * * * *