WO1998008439A1

WO1998008439A1 - Apparatus for the iris acquiring images

Info

Publication number: WO1998008439A1
Application number: PCT/US1997/014873
Authority: WO
Inventors: Michael Negin; Thomas A. Chmielewski, Jr.; Robin Sainsbury; Marcos Salganicoff; Keith James Hanna; Robert Mandelbaum; Deepam Mishra
Original assignee: Sensar, Inc.; The Sarnoff Corporation
Priority date: 1996-08-25
Filing date: 1997-08-22
Publication date: 1998-03-05
Also published as: CA2264029A1; EP0959769A1; AU4328297A; AU727389B2; KR20000035840A; KR100342159B1; JP2004073880A; JP2002514098A

Abstract

At least one wide field of view camera (3) and with an associated illuminator (6, 10) obtains sufficient images of a person to be identified so that x, y, z coordinates can be established for the expected position of that person's eye. The coordinates are used to direct a narrow field of view camera (16) and associated illuminators (21-23) to take an image of the eye (76, 78) that can be used for to identifying the person using iris verification and recognition algorithms. These illuminators are positioned and illuminated to eliminate or minimize specularities and reflections that obscure the iris (76).

Description

TITLE

APPARATUS FOR THE IRIS ACQUIRING IMAGES

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method and apparatus for illuminating the eye

to obtain an image of the iris.

2. Background of the Invention

There are several methods known as biometrics for recognizing or

identifying an individual. These methods include analyzing a signature, obtaining and

analyzing an image of a fingerprint and imaging and analyzing the retinal vascular

patterns of a human eye. Recently the art has used the iris of the eye which contains a

highly detailed pattern that is unique for each individual and stable over many years

as a non-contact, non-obtrusive biometric. This technique is described in United States

Patent No. 4.641 ,349 to Flom et al. and United States Patent No. 5,291 ,560 to

Daugman. The systems described in these references require the person being

identified to hold at least one of their eyes in a fixed position with respect to an imaging

camera which takes a picture of the iris. While this procedure is satisfactory for some

applications, it is not satisfactory for quick transactional activities such as using an

automated teller machine, unobtrusive access control or automated dispensing. Other

examples are immigration control, point of sale verification, welfare check dispensing,

internet banking, bank loan or account opening and other financial transactions. The iris identification techniques disclosed by Flom and Daugman

require a clear, well-focused image of the iris portion of the eye. Once that image is

obtained a comparison of that image with a coded file image of the iris of the person to

be identified can be accomplished quite rapidly. However, prior to the present

invention there has not been an optical system which could rapidly acquire a

sufficiently clear image of an iris of the person to be identified unless that person

positioned his eye in a fixed position relatively close to an imaging camera. There is a

need for a system which will rapidly obtain a clear picture of the iris of a person or

animal remotely from the optical system and in an uncertain position. This system

would be particularly useful to identify users of automated teller machines as well as

individuals seeking access to a restricted area or facility or other applications requiring

user identification. The system could also be used to identify patients, criminal

suspects and others who are unable or unwilling to be otherwise identified.

Automated teller machines, often called ATMs, are widely used for

banking transactions. Users are accustomed to receiving relatively fast verification of

their identity after inserting their identification card and entering an identification

number. However, anyone who knows the identification number associated with a

given card can use that card. Should a robber learn the identification number by

watching the owner use the card, finding the number written on the card or otherwise,

he can easily draw funds from the owner's account. Consequently, banks have been

searching for other more reliable ways of verifying the identity of ATM users. Since the iris identification methods disclosed by Flom et al. have

proved to be very reliable, the use of iris identification to verify the identity of ATM

users and other remote user recognition or verification application has been proposed.

However, for such use to be commercially available, there must be a rapid, reliable and

unobtrusive way to obtain iris images of sufficient resolution to permit verification and

recognition from an ATM user standing in front of the teller machine. To require the

user to position his head a predetermined distance from the camera, such as by using an

eyepiece or other fixture or without fixturing is impractical. Thus, there is a need for a

system which rapidly locates the iris of an ATM user and obtains a quality image of the

iris that can be used for verification and identification. This system should be suitable

for use in combination with an access card or without such a card. The system should

also be able to obtain such an image from users who are wearing eyeglasses or contact

lenses or ski masks or other occluding apparel.

SUMMARY OF THE INVENTION We provide a method and apparatus which can obtain a clear image of

an iris of a person to be identified whose head is located in front of the portion of our

optical system which receives light reflected from the iris. The system includes at least

one camera with or without ambient illumination and preferably at least one or more

illuminators. We also prefer to provide a pan/tilt mirror, or gimbal device and at least

one lens. Light reflected from the subject is captured by the gimbaled camera or mirror

and directed through the lens to the camera. In a preferred embodiment, a narrow field

of view (NFOV) camera receives the light reflected from the pan/tilt mirror through the lens or directly via a gimbaled mounted camera. A second camera and preferably a

third camera are provided to obtain a wide field of view (WFOV) image of the subject.

In some cases, the WFOV cameras may be superfluous, if the user is always known to

be in the field of view of the NFOV camera or could be located by moving the NFOV

camera. Images from these WFOV cameras are processed to determine the coordinates

of the specific location of interest, such as the head and shoulders and the iris of a

person to be identified. Based upon an analysis of those images the pan/tilt mirror or

gimbal is adjusted to receive light reflected from the iris or other area of interest and

direct that reflected light to a narrow field of view camera. That camera produces an

image of sufficient quality to permit iris identification.

The preferred embodiment contains a wide field of view illuminator

which illuminates the face of the person to be identified. The illuminator preferably

contains a plurality of infrared light emitting diodes positioned around the lens of the

wide field of view camera or cameras.

We also prefer to provide two or more narrow field of view illuminators

each comprised of an array of light emitting diodes. These arrays are mounted so as to

be rotatable about both a horizontal axis and a vertical axis. By using at least two

arrays we are able to compensate for specular reflection and reflection from eyeglasses

or contact lenses or other artifacts which obscure portions of the iris.

We further prefer to construct the arrays so that one set of light emitting

diodes have center lines normal to the base, a second set of light emitting diodes have

centerlines at an acute angle to the base, and a third set of light emitting diodes have centerlines at an obtuse angle relative to the base. This provides the array a wider field

of illumination. We further prefer to provide a control system which enables us to

separately illuminate each group of light emitting diodes. The control system may

permit selective activation of individual diodes. An alternative is to provide a single

illumination that is directed in a coordinated manner with the image steering device.

An image processor is provided to analyze the images from the wide

field of view camera and thereby specify the location of a point or area of interest on

the object or person being identified. A preferred technique for identifying the position

of the user is stereographic image analysis. Alternatively, visible or non-visible range

imaging or distance finding devices such as ultrasonic, radar, spread spectrum

microwave or thermal imaging or sensing or other optical means could be used.

The present system is particularly useful for verifying the identity of

users of automated teller machines. The system can be readily combined with most

conventional automated teller machines and many other financial transaction machines.

Image acquisition and identification can generally be accomplished in less than five

seconds and in less than two seconds in many cases.

Other configurations of cameras such as one NFOV camera, one WFOV

and one NFOV camera, two NFOV cameras, multiple NFOV cameras and multiple

WFOV cameras can be utilized for other special purpose applications such as more or

less restricted movement or position scenarios. For example, iris imaging in a

telephone booth or for a telephone hands free use, multiple iris imaging in a crowd of people, iris imagining of people in a moving or stationary vehicle, iris imaging of a race

horse, or a point of sale site use.

Other objects and advantages will become apparent from a description of

certain present preferred embodiments shown in the drawings.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a front view of a present preferred embodiment of our device

for obtaining images of irises.

Figure 2 is a side view of the embodiment of Figure 1.

Figure 3 is a top plan view of a first present preferred embodiment of our

narrow field of view illuminator.

Figure 4 is a side view of the illuminator of Figure 3 with the area of

illumination shown in chainline.

Figure 5 is a side view similar to Figure 4 of a second present preferred

embodiment of our narrow field of view illuminator.

Figure 6 is top view of a first present preferred illuminator bracket.

Figure 7 is a side view showing the illuminator bracket of Figure 6 with

the position of the illuminator shown in chainline.

Figure 8 is top view of a second present preferred illuminator bracket

Figure 9 is a side view showing the illuminator bracket of Figure 8 with

the position of the illuminator shown in chainline.

Figure 10 is a block diagram showing a preferred control architecture for

the embodiment of Figure 1. Figure 1 1 is a front view showing the eyes and glasses of the person to

be identified on which a reflection of the wide field of view illuminator appears.

Figure 12 is a front view showing the eyes and glasses of the person to

be identified on which a reflection from the narrow field of view illuminators appears.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to Figures 1 and 2 a present preferred embodiment of our

device is contained in housing 1 which is 14.5 inches wide, 15 inches high, and 18

inches deep. A housing of this size can be easily placed within or near an automated

teller machine or other limited access machine or entry place. When incorporated

within or placed near the housing of an automated teller machine our unit is located

behind a light transmissive bezel. Typically, the bezel would be smoked or other

visually opaque glass or a comparable plastic which obscures our device from being

easily seen. Our device would be positioned so as to be about eye level of most users.

In Figure 2 we show the head of a person to be identified user in front of our device.

In the preferred embodiment of our device shown in Figures 1 and 2, we

provide two wide field of view (WFOV) cameras 3 each having a lens 2 and 4. The

orientation and placement of lens 2 and 4 and other components may be changed to

accommodate available space or other applications. A wide field of view illuminator 6

surrounds the lens. Hoods 5 and 7 are provided around the lens 2 and 4 to prevent light

emitted from the illuminator 6 from passing directly into the camera. The wide field of

view illuminator is comprised of sets of light emitting diodes 10. For ease of construction, these sets of diodes may be mounted on small circuit boards 12. These

boards are then mounted on a housing 13 which surrounds the lens 2 and 4. A

sufficient number of LED containing circuit boards 12 are provided and positioned to

illuminate the head of the person to be identified who is standing in front of our device

as shown in Figure 2. Consequently, we prefer that the wide field of view illuminator

provide a field of illumination which encompasses a region of about two feet in

diameter at a distance of about one foot from the illuminator. This field of illumination

is indicated by the solid lines extending from the wide field of view illuminator 6 in

Figure 2.

Portions of the wide field of view illuminator are positioned around the

WFOV camera to provide nearly on-axis illumination. On axis illumination, nearly on

axis illumination, and oblique illuminator allow surface features to be imaged with

minimal shadows which can generate false edges or other artifacts. Such illumination

of the eye produces a shadow free image with good surface features. This type of

lighting may cause the pupil to be bright making the iris easier to locate although this

feature can be disabled if desired. Any shadows produced by other light sources and

camera angles are minimized or washed out. Illumination control of this type can be

used to stimulate parasympathetic autonomic nervous system reflexes that cause eye

blinks or pupil variation or other reactions. These changes may be useful to determine

subject awareness to establish certain life signs and to reduce pupil size for improving

imaging resolution. Light from the wide field of view illuminator is reflected from the user's

face into the lens of the wide field of view camera lens 2 and 4. This enables the

WFOV cameras to create images from which an x, y, z coordinate location can be

determined for one of the user's eyes. The WFOV cameras may also be used to provide

security video images for monitoring transactions or other activities. We take an image

of the right eye. However, either the left eye or the right eye or both eyes can be

selected. The WFOV cameras could utilize a number of techniques such as stereo,

stereo with structured light, and depth from focus with or without structured light to

determine both the x-y location and distance to the object of interest. We prefer to use

stereo processing techniques which compare at least a portion of the images from the

two wide field of view cameras to determine the x, y, z coordinate locations. We can

also provide a gaze director 9 which assists in identifying the location and motion of the

eye, by attracting the attention of the user.

After we know the position of the selected eye we must illuminate the

iris portion of the eye and obtain an iris image which can be used for iris verification

and recognition. We prefer to be able to obtain an image having approximately 200

pixels across the iris portion of the image so that the image recognition algorithms used

to perform identification and verification can operate reliably.

The iris recognition algorithms compare features of the iris in the image

with the same features in a file image. Verification is considered to have been made

when there is a match of a predetermined number of the compared features. For some

situations a match of at least 75% of the compared features may be required. It is therefore important that there be no specularities, spurious light reflections or dark

shadows covering a significant portion of the image. When the user is wearing glasses,

this can easily occur. To overcome this problem we provide at least two spaced apart

illuminators for use in conjunction with the NFOV camera. These illuminators in

conjunction with the WFOV camera may be selectively switched to an orchestrated

combination to enhance these image structures. For example, a structured specularity

can be created on eyeglasses to make eye finding easier, and then disabled for iris

image acquisition.

In the embodiment shown in Figure 1 a single NFOV camera 16 is

positioned behind mirror 18. Light emitted from one or more of the NFOV

illuminators 21 , 22 or 23 is reflected from the selected eye to an optical subsystem 30

which directs the reflected light to the NFOV camera. Wc can provide a sensor 14

which senses the level of ambient light surrounding the person to be identified.

Information from this sensor can be used to determine what, if any, illumination must

be provided by the illuminators 21,22 and 23. Alternatively, any one or a plurality of

cameras themselves may be used for such light sensing.

The optical subsystem 30 in the embodiment shown in Figure 1 contains

a pan/tilt mirror attached to rod 33 which extends from motor 34. This enables the

pan/tilt mirror to be rotated about a tilt axis corresponding to a centerline through rod

33. Motor 34 is mounted on arm 35 which is pivotably attached to base 36 by rod 37.

This arm 35 can be moved around a pan axis corresponding to a centerline through rod

37. Light emitted from any of the NFOV illuminators 21 , 22, or 23 is reflected from the subject iris to the pan/tilt mirror 32. That mirror is positioned to direct the reflected

light to mirror 18 from which the light is reflected to NFOV camera 16. The lens of the

NFOV camera can be moved to change the focus or zoom, and the aperture of the

camera is adjustable. One can also mount NFOV camera 16 on a movable platform so

that the NFOV camera can be turned toward the eye. Then, the portions of the optical

subsection shown in Figure 1 may not be needed. Our preferred optical subsystem has

five degrees of freedom: the pan axis, the tilt axis, the focus axis, the aperture axis and the zoom axis. A system with fewer degrees of freedom could also be used. The pan

and tilt axes are used to position the pan/tilt mirror 32 so that the correct narrow field is

imaged onto the sensing array of NFOV camera 16. The ability to control movements

along the focus axis, aperture axis and zoom axis allows us to be certain that the imaged

object is in focus. In some cases, only the NFOV camera is needed and the WFOV

camera may optionally not be used.

The design of the optics resolution, magnification, focusing and size of

the imager dictates the distance between the camera and lens and the distance between

the lens and object to be imaged. The size of the imager is of paramount importance in

defining the distance from lens to imager and contributes to the depth of focus. Those

versed in the art will recognize that NFOV camera 16 may be solid state or of vidicon

nature and that the sensing array size can vary from generic industry sizes of 1/4, 1/3,

1/2, 2/3 or 1 inch diagonal measurement. In an optical system, the introduction of a

mirror in an optical path allows the path to be redirected without effecting the optical

path length. The use of these mirrors allows the optical path to be folded back on itself thus reducing the overall required physical length needed to implement the optical

design. Those skilled in the art will recognize that a gimbaled camera can also be used

to perform image steering.

In the embodiment of Figure 1 the illuminators are positioned to provide

a field of illumination illustrated by the dotted lines in Figure 2. These fields must be

directed and sized so that light will be reflected from the eye of the user to the pan/tilt

mirror 32. To achieve this result we provide three illuminators 21 , 22 and 23 placed at

different locations on the housing 1. These illuminators arc oriented to direct light to

the areas where the user's eye is most likely to be based upon information received from

the WFOV cameras or other position detectors that could be used. The illuminators

may be mounted in a permanent location and orientation or placed on manually

adjustable or motorized brackets such as those shown in Figures 6, 7, 8 and 9. The

illuminators could also be attached to a sliding mechanism for translation along an axis.

The light source preferably is a light emitting diode or other device that

emits infrared or near infrared light or a combination of these. A lens and diffuser (not

shown) can be used to guarantee uniform illumination. We have found infrared light to

be particularly useful because it penetrates eyeglasses and sunglasses more easily than

visible light or colored light within the visible spectrum. Infrared light is also invisible

to the user and extremely unobtrusive. Optical filters may be placed in the light path in

front of the camera to reduce any undesirable ambient light wavelengths that corrupt

the desired images. Different wavelength priority filters may be used to permit

different wavelengths to be used to optimize each camera's performance. For example, longer wave IR could be used for WFOV camera imaging and shorter IR could be used

for NFOV camera imaging. Then the NFOV cameras would not respond to WFOV

illumination. This "speed of light" processing can be used to great advantage. If

desired, the LED light source could be strobed. Strobing provides the capability to

freeze motion. Strobing also provides the capability to overwhelm ambient light by

using a high intensity source for a brief period of time, and exposing the camera

accordingly to wash out the background ambient illumination which would otherwise

cause interference. Strobing NFOV and WFOV illuminators, perhaps at different

times, and allowing the cameras to integrate photos over appropriate, possibly

disparate, time slices permits optimum usage of the specific spatial and time

characteristics of each device.

As shown in Figure 1, 3, 4 and 5, the NFOV illuminators are preferably

comprised of a 6 x 6 array of light emitting diodes 20 mounted on a circuit board 24. If

the light emitting diodes are mounted normal to the circuit board the illuminator will

illuminate an area of illumination having some diameter b as indicated in Figure 4. We

have discovered that the area of illumination can be increased using the exact same

components as are used for the illuminator of Figure 4 by repositioning or otherwise

reconfiguring the light emitting diodes. This is shown in the embodiment of Figure 5

by larger diameter a. In that illuminator the top two rows of diodes are positioned at an

acute angle relative to the board 24 and the lower two rows of diodes are mounted at an

obtuse angle. Circular ring illuminators or other shapes may also be used which could

be placed around the NFOV lens. Other optical elements such as polarizers or birefringent analysis devices may be used to minimize artifacts or enhance other

biologically relevant characteristics such as corneal curvature, eye separation, iris

diameter, skin reflectance and sclerac vasculature.

In Figures 6 and 7 we show a bracket which we have used to attach the

NFOV illuminators 21, 22, and 23 to the housing 1. That bracket 30 has a U-shaped

base 31 having a hole 32 through which a screw attaches the bracket to the housing. A

first pair of gripper arms 33 and 34 with attached pin 42 are pivotably attached to one

upright of the base. A similar second pair of gripper arms 33 and 34 are pivotably

connected to the opposite upright through collar 37. The illuminator indicated in chain

line in Figure 7 is held between the gripper arms by screws or pins 38. A series of

holes (not visible) are provided along the uprights so that the gripper arms can be

positioned at any selected one of several positions. A locking tab 39 extends from the

collar 37 into an adjacent slot in the upright to prevent rotation of the collar. Set screw

38 is tightened against the pin 42 extending from gripper arms 35 and 36 to prevent

rotation of the gripper arms.

A second bracket 44 which we have used to attach the NFOV illuminators 21, 22, and 23 to the housing 1 is shown in Figures 8 and 9. That bracket

50 has a base 51 which attaches to the housing. A rod 52 extends upward from the

base 51. Collar 53 slides along rod 52 and can be held at any desired location on the

rod by set screw 54. Rod 55 extends from collar 53 and holds carrier 56. This carrier is

slidably attached to the rod 55 in the same manner as collar 53. The illuminator

indicated in chain line in Figure 9 is attached to the carrier 56 by fasteners or snap fit on pins 57 extending from the carrier. Both this bracket 50 and the other illustrated

bracket 30 permit the attached illuminator to be repositioned or adjusted along a pan

axis and a tilt axis.

We prefer to connect each array of light emitting diodes through a

distribution board 60 to an illumination controller 62 as shown in Figure 10. Since there

can be one or more illuminator arrays these arrays are designated as ILLUMINATOR 1

through ILLUMINATOR X in the drawing. The distribution board 60 and illumination

controller 62 enable us to selectively light the WFOV illuminator 6 and the NFOV

illuminators 21 , 22 and 23 in the embodiment of Figure 1. Furthermore, we can

selectively illuminate sets of light emitting diodes within each array or selectively light

individual diodes.

Each set of light emitting diodes may emit a different wavelength of

light. It has been noted that the irises of different people respond better to certain

wavelengths and worse to other wavelengths of light. This could be accomplished

using illuminators with different wavelength LEDs or populating a single illuminator

with different wavelength LEDs next to each other. These could be strobed and the

better image selected. Additionally, LEDs of different beam widths could be mounted

side by side or in different illuminators for illumination intensity control or for

specularity control - the higher tighter the beamwidth the less the size of the

specularity.

We can also control the duration and the intensity of the light which is

emitted. To prevent burnout of the illuminators caused by prolonged illumination we can provide timers 63 for each illuminator as indicated by the dotted blocks labeled "T"

in Figure 10. The timers will cut the power to the array after a predetermined period of

illumination. The WFOV cameras 3 provide images to an image processor 64 which

we call the PV-I. That processor 64 tells the computer 65 the x, y, z coordinates of the

selected eye or eyes of the person to be identified. The image processor may also

assess the quality of the image and contain algorithms that compensate for motion of

the subject. This processor may also perform image enhancement. The PC 65 has

access to information from the ambient light level detector 69 and the NFOV camera.

These data can be used to modify illumination strategies. The x, y, z coordinates for

the expected position of the eye enable the computer to direct the illumination

controller as to which illuminators should be lighted and to direct the pan/tilt controller

66 to properly position the pan/tilt unit 67 so that a useful image of the iris can be

obtained. These functions may be selected by results from the WFOV camera

processing. Commands are sent from the computer 65 to the motors to change the

location of the pan/tilt axes or to adjust focus. In the simplest case, one may consider

that a WFOV image is acquired, the data is processed and then passed through the

image processor 64 and computer 65 to the pan/tilt controller 66 or a gimbaled

controller. In order to minimize motion time and control settling time, there can be

simultaneous motion in the optical subsystem along all five axes.

The pan/tilt controller 66 accepts macro level commands from the

computer and generates the proper set points and/or commands for use by the

illumination control or each axis supervisor. The intermediate continuous path set points for the axis are generated here and then sent to each axis supervisory controller.

A command interpreter decodes the commands from the image analysis and formats

responses using positioning information from the optical devices. A real time interrupt

produces a known clock signal every n milliseconds. This signal is a requirement for

the implementation of a sampled data system for the position controller of each axis

and allows synchronization via the supervisory controller for continuous path motion.

A diagnostic subsystem performs health checks for the control system.

Besides the choreography of the five axes, the microprocessor controller

must also provide illumination control. The illumination controller will accept

commands similar to the commands associated with motion control to timely activate,

or to synchronously activate with the camera frame taking, selected illuminators.

Images from the WFOV are transmitted as analog signals to the image

processor 64. The image processor preferably contains two pyramid processors, a

memory capable of storing at least two frames, one LUT, ALU device, a digitizer

which digitizes the analog video signal, a Texas Instrument TMS 320 C-31 or C-32

processor and a serial/parallel processor. The image is processed using the pyramid

processors as described in United States Patent No. 5,359,574 to van der Wal. The

Texas Instruments processor computes disparities between images. The WFOV images

defines a region or point in the field of view of the WFOV cameras where the subject's

right eye or left eye or both are located. Using stereo processing techniques on the

disparities will result in x, y, z coordinates for points on the subject relative to the

WFOV cameras. That information is then further processed to define an area of interest such as the head or an eye. The coordinates of the area of interest are used to direct the

NFOV optical system. These position coordinates are transferred from the image

processor to a NFOV image and iris image processor 65. This unit 65 contains a 486,

PENTIUM or other microprocessor system and associated memory. In the memory are

programs and algorithms for directing the optical platform and doing iris identification.

Additionally, WFOV video images can be stored as a security video record.

The focus axes of the NFOV system may be controlled in an open loop

fashion. In this case, the x,y,z coordinate from stereo processing defines via table look

or analytic computation the focus axis position so that the lens properly focuses the

NFOV camera on the object of interest. A closed loop focus method could also be

used. In this case, NFOV video would be processed by image processor 64 to obtain a

figure of merit defining if the axis was in focus. From the figure of merit the axis could

be commanded forward or backward and then a new image acquired. The process

would continue in a closed loop form until the image is in focus. Other information

such as iris size and location as measured in camera units, and eye separation from

WFOV camera images can be combined with stereo and other focus information into

multivariate features than can be used to refine range information by fusion of direct or

derived sensory information. This sensor fusion may encompass other information as

well.

Since the object of interest, namely the eye, may be moving, there is a

requirement that the NFOV camera track the trajectory seen by the WFOV. When

motion ceases to blur the image, a quality image may be acquired via the NFOV camera and optics. By tracking the eye, the optics directing light to the NFOV camera are

aligned so that when it is desired to obtain an iris quality image little or no additional

motion may be required.

In this case, the x,y,z coordinates from analysis of the WFOV images are

sent to the NFOV controller at some uniform sample rate (such as every 100 ms). A

continuous path algorithm such as described in Robotic Engineering An Integrated

Approach, by Klafter, Chmielewski and Negin (Prentice Hall, 1989) would be used to

provide intermediate sets of {p,t,f,a,z} set points to the axis so that the axes remain in

motion during the tracking phase. To define the last end position, either a macro level

command can be given or the same {p,t,f,a,z} can be continually sent at the sample

periods.

It is important to recognize that as the NFOV axes move, the associated

imager may not have sufficient time to perform the required integration to get a non-

blurred image. Additionally, depending on the camera used (interlaced or progressive

scan) there may be field to field displacement or horizontal displacement of the image

all of which can be wholly or partially corrected by computation. Thus, it is easily seen

why the WFOV camera provides the information necessary for directing the NFOV

stage. It should be noted, that certain eye tracking algorithms (such as those based on

specularity or iris configuration or pattern matching) may be capable of providing

sufficient information (even if the image is slightly blurred due to focus or exhibits

some blur caused by motion) to provide a reasonable estimate of the eye location in the

NFOV camera. Hence, it is conceptually possible to use the WFOV data for coarse movement and the processed NFOV data (during motion) as additional information for

finer resolution. This fusion of data can provide a better estimate than one WFOV

camera image alone in positioning the NFOV image to acquire a quality iris image.

To acquire a quality iris image, the NFOV axes must settle to a point

where the residual motion is less than that which can be delected by the imager. Once

this occurs, any remaining images must be purged from the imager (typically there is a

delay between an image integrated and the readout via RSI 70) and the proper

integration time allowed to acquire a non blurred image. See Robotic Engineering An

Integrated Approach for a timing scenario. This can be accomplished in a number of

ways, the simplest being a time delay which occurs after the cessation of motion until a

good quality RSI 70 image is captured. Multiple iris images which may be partially

obscured may be collected and fused into a single composite, less obscured iris image

using normalization and fusion methods.

We have found that any light source will cause a reflection on eyeglasses

of the person to be identified. The eyes as seen from the WFOV cameras 3 are shown

in Figure 11. There is a reflection 70 from the WFOV illuminator 6 on both lenses 72

of the person's eyeglasses 74. The reflection 70 partially covers the iris 76 of the

person's eye making iris identification difficult if not impossible. To overcome this

problem we use illuminators 21, 22 and 23 located off-axis from the optical axis of the

NFOV camera 16. By carefully positioning and sometimes using only some of the

light emitting diodes we can achieve adequate illumination without creating an

obscuring reflection. This result is shown in Figure 12 where light from only a few light emitting diodes in the NFOV illuminators 21 , 22 and 23 has created a reflection

80 that appears in the image. That reflection does not cover any part of the iris 76. In

some cases especially with glasses, the WFOV specularity makes finding the head and

the eye more expeditious.

Multiple illuminators also enable us to determine the shape of eyeglasses

worn by the subject in the images. We illuminate the eyeglasses sequentially using two

spaced apart illuminators. The specularity will be in one position during the first

illumination and in a different position during the second illumination. The amount of

specularity change is then calculated to determine appropriate eyeglass shape. From

that information we can determine the minimum movement of illumination required to

move the specularity off of the iris.

A calibration procedure must be used to correlate the center of the

NFOV camera's field of view with pan/tilt and focus axis positions for a series of

coordinates in 3 dimensional space as defined by the wide field of view. Given a set of

WFOV coordinates {x,y,z} defining the position of a user's eye somewhere in the

working volume in front of the cameras, a transformation or table look up can be used

to define the coordinates of the pan, tilt and focus {p,t,f} axes that make the center of

the NFOV camera's field of view coincident with x,y coordinates and in focus on the z

plane. We prefer to use a series of targets to assist in calibration. These targets have

partially filled circles corresponding to iris positions at known locations on a page. The

targets are placed a known distance from the housing and the device is activated to

attempt to find an iris and produce a calibration image. When NFOV and WFOV cameras are used, they must be calibrated

together. This may be accomplished by manual or automatic procedures, optical targets

or projected targets may be used. An automatic procedure would require a calibration

object to be automatically recognized by the computational support equipment

operating on the camera images. Another possibility is to use the NFOV camera

motion capabilities or other motion generation capability to project a target into the

calibration volume, and then recognize the target.

Although we have shown certain present preferred embodiments of our

compact image steering and focusing device and methods of using that device, it should

be distinctly understood that our invention is not limited thereto but may be variously

embodied within the scope of the following claims.

Claims

We Claim:

1. An apparatus for acquiring images of irises comprising:

at least one camera positioned to take an image of an eye so that the

image will contain a representation of the iris which is of sufficient resolution to be

used for iris verification and identification; and

at least one illuminator positioned to illuminate the iris and comprised

of a plurality of light emitting elements which can be selectively illuminated and

concurrently illuminated.

2. The apparatus of claim 1 also comprising a second illuminator

positioned to illuminate the iris, the second illuminator being positioned apart from the

first illuminator.

3. The apparatus of claim 2 wherein the second illuminator is comprised

of a plurality of light emitting elements which can be selectively illuminated.

4. The apparatus of claim 1 wherein light is reflected from the iris to the

at least one camera along a camera axis and the light travels from the at least one

illuminator along a path which intersects the camera axis.

5. The apparatus of claim 1 wherein the at least one illuminator is

comprised of at least one array of light emitting diodes mounted on a base.

6. The apparatus of claim 5 wherein the array of light emitting diodes is

comprised of:

a. a first set of light emitting diodes which is attached to the base in a

manner to emit light along a first path; and

a second set of light emitting diodes which is attached to the base in a

manner to emit light along a second path which is not parallel to the first path.

7. The apparatus of claim 5 wherein the first set of light emitting diodes

and the second set of light emitting diodes can be separately illuminated.

8. The apparatus of claim 5 also comprising an array bracket to which

the base of the at least one array of light emitting diodes is pivotally attached for

rotation about an array axis.

9. The apparatus of claim 8 also comprising a second bracket to which

the array bracket is movably attached in a manner to permit movement of the array

along a line normal to the array axis.

10. The apparatus of claim 5 wherein at least some of the light emitting

diodes emit light of a wavelength which is different from light wavelengths emitted

from other light emitting diodes.

1 1. The apparatus of claim 1 wherein the at least one illuminator can

emit at least one of infrared light, visible light, near infrared light, a select band of light

frequencies, and both visible light and infrared light.

12. The apparatus of claim 1 the at least one illuminator can emit light

of varying intensity.

13. The apparatus of claim 12 also comprising a power source

connected to the at least one illuminator which can emit light of varying intensity and a

controller connected to the power source for changing power output to the at least one

illuminator thereby changing intensity of the light which is emitted by that illuminator.

14. The apparatus of claim 1 wherein the at least one of the illuminators

can emit different wavelengths of light.

15. The apparatus of claim 2 also comprising a controller connected to

the at least one illuminator and the second illuminator, the controller containing a program for selectively illuminating the illuminators according to a dynamically

predetermined pattern.

16. The apparatus of claim 1 also comprising a wide field of view

camera positioned to take an image which includes the eye.

17. The apparatus of claim 16 also comprising a wide field of view

illuminator.

18. The apparatus of claim 17 wherein the wide field of view

illuminator is comprised of a ring of light emitting elements arranged around the wide

field of view camera.

19. The apparatus of claim 17 also comprising a hood surrounding the

wide field of view camera to prevent light from the illuminators from directly entering

the camera.

20. The apparatus of claim 1 also comprising a power source connected

to the at least one of the illuminators and a timer connected to the power supply which

timer turns off the power source after a selected period of time.

21. The apparatus of claim 1 also comprising an ambient light sensor

and a controller connected to the ambient light sensor and the at least one illuminator

the controller containing a program for shutting off the illuminators when the ambient

light is at a predetermined level.

22. The apparatus of claim 1 also comprising a motor connected to the

at least one illuminator.

23. The apparatus of claim 1 also comprising an optical system which

receives light reflected from the iris and directs the light to the at least one camera.

24. The apparatus of claim 1 wherein the at least one camera is movable.

25. A method for acquiring an image of an iris comprising the steps of:

locating a three dimensional coordinate position of an eye containing the

iris to be imaged;

positioning a camera so that at least some light reflected from the iris

will be reflected to the camera;

illuminating the eye with at least one illuminator so that light is reflected

from the iris to the camera along a camera axis and the light travels from the at least

one illuminator along at least one path which intersects the camera axis wherein the at least one illuminator is comprised of a plurality of light emitting elements which can be

selectively illuminated; and

creating at least one image of the iris with the camera during

illumination which image is of sufficient resolution to be used for iris verification and

identification.

26. The method of claim 25 wherein the at least one illuminator is

comprised of a first illuminator and a second illuminator which are illuminated

sequentially and the camera creates a first image and a second image during the

sequential illumination which images are used to create the image of sufficient

resolution to distinguish among identifying features within the iris.

27. The method of claim 25 wherein the at least one illuminator is

comprised of two sets each set containing a plurality of light emitting elements which

sets are selectively and sequentially illuminated .

28. The method of claim 25 wherein the at least illuminator can emit at

least one of infrared light, visible light, near infrared light, a select band of light

frequencies, and both visible light and infrared light.

29. The method of claim 25 wherein the image is comprised of a

plurality of pixels and that portion of the image which contains the iris is comprised of

at least 200 pixels.

30. The method of claim 25 wherein the three dimensional coordinate

position of the eye is located by :

a. using a first wide field of view camera to create a first image

of a region in which the eye is believed to be located;

b. using a second wide field of view camera spaced apart from

the first wide field of view camera to create a second image of a region in which

the eye is believed to be located; and

c. combining the first image and the second image in a manner

to establish the three dimensional coordinate position of the eye.

31. The method of claim 30 wherein the images are combined using

stereographic image analysis.

32. The method of claim 30 also comprising the step of illuminating the

region using nearly on axis illumination.

33. The method of claim 25 wherein the camera is mounted within an

optical subsystem containing a pan/tilt mirror from which reflected light is directed to the camera and also comprising the step of adjusting the pan/tilt mirror toward

the three dimensional coordinate position of the eye to direct light reflected from

the iris to the camera.

34. The method of claim 25 wherein the camera is gimbal mounted and

also comprising the step of adjusting the camera toward the three dimensional

coordinate position of the eye to direct light reflected from the iris to the camera.