CN101099164A - Post processing of iris images to increase image quality - Google Patents
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- CN101099164A CN101099164A CNA2005800460413A CN200580046041A CN101099164A CN 101099164 A CN101099164 A CN 101099164A CN A2005800460413 A CNA2005800460413 A CN A2005800460413A CN 200580046041 A CN200580046041 A CN 200580046041A CN 101099164 A CN101099164 A CN 101099164A
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Abstract
A rapid iris acquisition, tracking, and imaging system can be used at longer standoff distances and over larger capture volumes, without the active cooperation of subjects. The captured iris images can be used for biometric identification. Light illuminates the subjects' eyes. Reflections from the eyes are used to steer a high resolution camera to the eyes in order to capture images of the irises.
Description
The cross reference of related application
The application's case advocate based on 35 U.S.C. § 119 (e) on February 17th, 1 applied for be entitled as " BiometricIdentification and Iris Imaging Using Retinal Retro-Reflection " the 60/654th, the right of priority of the 60/634th, No. 331 U.S. Provisional Patent Application case that is entitled as " Adaptive Optics (AO) Imaging Applied toBiometric Identification Using Iris Imaging " of No. 638 U.S. Provisional Patent Application cases and application on Dec 7th, 2004.The purport of all above-mentioned temporary patent application cases is incorporated herein by reference in full.
Technical field
The present invention relates to for example to can be used for the imaging of the human iris of bio-identification.
Background technology
Be difficult to adapt to the technology of development along with the individual identification of traditional form becomes, gradually bio-identification be considered as the feasible method of individual identification.The technology of for example speech recognition, fingerprint recognition and iris imaging depends on the personal touch on the health that is difficult to change or duplicates.
Yet, carry out the high-definition picture that bio-identification needs iris usually by iris imaging, make the necessary fine detail of certain identification so that analyze.Required as identifying purpose, the iris image that need have about 200 microns or better spatial resolution is usually distinguished the meticulous myoarchitecture of human iris uniquely.In the system of person under inspection's active cooperation, for example the condition of illumination geometry, camera resolution, time shutter and optical wavelength can be optimised, so that capture the high-contrast image of the fine structure of iris.Existing system needs the person under inspection that its head is remained on ad-hoc location usually, stares the iris imaging camera from close proximity and in approximate orientation head-on simultaneously.Although the iris imaging aspect makes progress at present, the task of capturing enough high-definition pictures of human iris still needs the active cooperation of person under inspection's certain degree usually.
For instance, (for example, 5,000,000 pixels) system will have the visual field of about 15cm usually at the projection scope place of 1m, produce the about 75 microns spatial resolution of each pixel at the projection scope place of 1m to use commercial colored CCD technology.Therefore, the person under inspection must be in about 1m scope of camera, and its Iris Location must be continued the sufficiently long period in the 15cm visual field, so that make camera focus on and capture the image of the suitable resolution of iris.This requires person under inspection's active cooperation usually.Become obviously even worse penetrating the distance situation than far throw.For instance, if use same camera at the projection distance place of 10m, keep identical angular resolution will cause the spatial resolution of each pixel 750 μ m so, this is unacceptable.On the other hand, keep the spatial resolution of each pixel 75 μ m will cause the wide visual field of 15cm at 10m place.Iris remained in this visual field also be difficult to.
" capture volume " of iris imaging system is that the iris imaging system can capture enough volumes of high-resolution iris image in the above.Above-mentioned system and other similar legacy system based on CCD has less capture volume, it is too little and make traditional iris imaging system not be suitable for the situation of non-cooperation, for example for the people of big group, the iris imaging used on longer projection distance or for hidden identification.For instance, may be desirably in pass by inlet (for example, metal detector) or locate to capture person under inspection's iris image of person under inspection in for example airport, railway station, crossing, border, building safety import etc.High resolving power and longer projection distance during these are used require to have brought the unappeasable very big challenge of current design to the iris imaging system.The capture volume of current iris imaging system and projection distance ability are big inadequately so that can effectively handle the situation of these types.
Therefore, need have big capture volume and/or the iris imaging system that distance is used can penetrated than far throw.
Summary of the invention
The limitation of the present invention by providing a kind of quick iris imaging system to overcome prior art can be used described quick iris imaging system at longer projection distance place and on big capture volume, and without person under inspection's active cooperation.The bright person under inspection's of illumination eyes.Use makes the high resolving power camera turn to (and preferably also focusing on) eyes from the reflection (for example, reflecting from amphiblestroid retroeflection or from the flash of light of cornea) of eyes, so that capture the image of iris.Turn in real time with convergence correction to prolong the available time shutter, therefore under than the lower illuminance of other possibility situation, realize good image.Also can be at other method of real-time controlling Design to turning to and focusing on.
In one embodiment, the iris imaging system comprises imaging subsystems.Imaging subsystems comprises camera, light source and meticulous tracker.Camera is captured the iris image with the enough resolution that is used for bio-identification.Light source produces the light that illuminates the eyes in the capture volume.Meticulous tracker makes camera turn to eyes based on the reflection (being preferably retroeflection or flash of light reflection) from eyes.
In one approach, meticulous tracker comprises the adaptive optics loop that is driven by reflected light.For instance, the adaptive optics loop can comprise deformable mirror, wavefront sensor and controller.Catoptrical wave front of wavefront sensor senses and controller drive deformable mirror based on the wave front that senses.Therefore the wave front that deformable mirror corrects is imported into makes camera turn to eyes (that is the correction of tip and sloping wavefront error).Deformable mirror also can make described camera focus on (that is the correction of focusing error).In this way, even without person under inspection's active cooperation, imaging subsystems also can obtain iris image.
The iris imaging system also can comprise and obtains subsystem, person under inspection's apparent position in its identification capture volume.For instance, wide field of view acquisition subsystem can be coupled with narrower view field imaging subsystem.Obtain subsystem identification person under inspection's apparent position, and imaging subsystems is turned back to next person under inspection from a person under inspection, to obtain the image of its iris.Described two subsystems of controller coordinate.In one approach, obtain subsystem based on the apparent position of discerning the person under inspection from the retroeflection of person under inspection's eyes.This is easily, because round-shaped permission of eye pupil easily will be distinguished from retroeflection and other light source of eyes.Described two subsystems can be partially or completely integrated.For instance, but its optical alignment makes it all facing to substantially identical direction, will have the visual field more much bigger than imaging subsystems usually but obtain subsystem.
Others of the present invention comprise the method corresponding to said apparatus and system.
Description of drawings
The present invention has other advantage and feature, when considered in conjunction with the accompanying drawings, from following to will be easier the detailed description of the present invention and appended claims understanding described advantage and feature, in the accompanying drawing:
Fig. 1 is the explanation according to iris imaging of the present invention system.
Fig. 2 is based on the explanation from another iris imaging system of the retroeflection of eyes according to of the present invention.
Fig. 3 is the explanation from the retroeflection of eyes.
Fig. 4 is the explanation of the typical reflectance spectrum of human eye.
Fig. 5 is based on the explanation from another iris imaging system of the flash of light of eyes according to of the present invention.
The graphic embodiments of the invention of only describing for purpose of explanation.The those skilled in the art will understand from following content of the discussions easily, under the situation that does not break away from principle of the present invention described herein, can adopt the structure that this paper illustrates and the alternate embodiment of method.
Embodiment
Fig. 1 is the explanation according to iris imaging of the present invention system.The iris imaging system comprises imaging subsystems 200, and optionally comprises and obtain subsystem 100.Described system through design on capture volume 50 greatly, to capture the iris image of many eyes 134 under the common situation in no person under inspection's active cooperation.In an application, the person under inspection is by import 60 (for example, gateway or metal detector), and capture volume 50 is the inlets that lead to import, and when the person under inspection passed through capture volume, the iris imaging system captured iris image.In many application, can define capture volume based on the stream of people's import or other bottleneck.Example comprises corridor, revolving door (turnstyle), tollbooth, elevator door, escalator and garage parking inlet.Other example comprises pay the bill mouth or other formation, crossing, side line and driveway.
This situation is " non-cooperation " normally, means person under inspection's active cooperation not in the iris imaging process.For instance, they do not place head device can capture iris image.In fact, they just walk by import, and when they did like this, system captured their iris image.They in addition may not know that system is capturing iris image.If secret is more important, wavelength should be chosen as non-visible so.
Different devices can be used as and obtains subsystem 100 and as imaging subsystems 200.Obtaining subsystem 100 also can follow the tracks of the person under inspection from the reflection of person under inspection's eyes based on using.Perhaps, it can be based on diverse mechanism.For instance, obtain the conventional digital picture that subsystem 100 may be captured described capture volume.Which of which part representative of each image that then uses software to discern to capture and/or everyone partly is its face or eyes.That can use frame and frame relatively follows the tracks of moving of person under inspection.Can use stero (based on eye reflections, conventional imaging or other method) triangulation subject positions in capture volume.
Among Fig. 1, be shown as single box with wide visual field 130 with obtaining subsystem 100.This only is a representative.Obtain subsystem 100 and be not limited to single box.In stereoscopic example, equipment is positioned at diverse location so that capture different points of view.Even do not use stereoscopic approach, still can advantageously use a plurality of cameras (for example) more effectively to cover whole capture volume 50.
Wide visual field 130 need not to implement fully as shown in Figure 1 equally.Each obtains camera can have the wide visual field that covers whole capture volume 50, as shown in Figure 1.Perhaps, each obtains camera can not exclusively cover whole capture volume 50, but described camera covers whole capture volume 50 together.In addition, camera may scan rather than watch attentively, and its instantaneous field of view may be less than capture volume 50.Any moment in time, the only sub-fraction of whole capture volume is capped, but along with whole capture volume of the past of time is capped.
As last example, obtaining subsystem 100 may be fully based on camera.Can use the position transducer of other type or invade the position that sensor is determined the person under inspection.For instance, capture volume 50 can be covered by grid of light beams.Make light beam disconnect determining person under inspection's position by the person under inspection.In diverse ways, can use the pressure pad that is installed on the floor to determine subject positions.Sonar, radar, laser radar and heat detect or imaging is the example that can be used for other technology of definite subject positions.For the sensor of some type, be enough to cover capture volume 50 as long as obtain subsystem 100, even can not use term " visual field ".
190 pairs of two subsystems of controller are coordinated.Imaging subsystems 200 (via controller 190) uses from the information of obtaining subsystem 100 roughly narrow visual field 230 is turned between the person under inspection.For obtaining subsystem 100, many different designs of imaging subsystems 200 also are possible.In one approach, use the conventional equipment of deviation mirror for example or universal joint that narrow visual field 230 is turned to person under inspection 134 roughly.Then use ADAPTIVE OPTICS SYSTEMS (Fig. 1 is not shown) to realize quick, meticulous tracking, and optionally also carry out focus adjustment to be used for image capture to person under inspection 134.ADAPTIVE OPTICS SYSTEMS is driven by the eye reflections from person under inspection's eyes 134 and/or drives by other position and distance measurement technique.Also can use other method.Risley prism (Risley prism), LCD phased array row, real-time holography and Bragg grating (Bragg grating) are the examples of other steering gear.Other signal source can comprise flash of light, use image or the parallax of eye reflections and the time of flight lidar.
Fig. 2 is according to the explanation that the present invention is based on from the exemplary iris imaging system of the retroeflection of eyes.In this example, obtain subsystem 100 and comprise light source 110, beam splitter 115, little " picking up " mirror 119 and camera 150.Imaging subsystems 200 comprises light source 210, beam splitter 215, deformable mirror 220, beam splitter 225, wavefront sensor 227 and controller 222.It also comprises light source 248 and camera 250.For simplicity, various light sources can be called and obtain light source 110, WFS light source 210 and iris imaging light source 248, to distinguish each other.The iris imaging system also comprises the rough tip-tilt deviation mirror (coarse tip-tilt steering mirror) 120 by controller 190 control, and it is as obtaining both parts of subsystem 100 and imaging subsystems 200.In Fig. 2, deviation mirror 120 is depicted as the line that passes light beam, but for simplicity, the reflection of not shown deviation mirror (that is, optical path launches with respect to deviation mirror 120).Use various lens (or other optical element) to the light beam that runs through system collimate, focusing, imaging or otherwise change and continue.
It is as follows to obtain subsystem 100 operations.Obtain the light source that light source 110 is cameras 150.Beam splitter 115 and mirror 119 are left in the light reflection that light source 110 produces.Beam splitter 115 is separated with retrieval system the light of the system of leaving that light source 110 produces with the light that is imaged onto on the camera 150.Beam splitter 115 can be a polarization beam splitter, and it can use to suppress backreflection and direct reflection with quarter wave plate.For low cost and simplicity, beam splitter 115 also can be neutral beam splitter (neutral beamsplitter) (that is a no polarization selectivity).Mirror 119 will obtain the optical path combination of subsystem 100 and imaging subsystems 200, so it is substantially along common optical axis alignment.In this example, two subsystems are operated with different wave length, so mirror 119 is to reflect wavelength that obtains subsystem 100 and the dichromatism beam splitter that passes through the wavelength of imaging subsystems 200.Follow reflection from the output illumination of light source 110 and leave rough deviation mirror 120 to illuminate the broad visual field 135 that obtains subsystem 100.Visual field 135 can be stared whole capture volume 50 or can scan on capture volume.In this example, visual field 135 is wide inadequately, so that can not stare the whole capture volume of covering under the pattern.In fact, it scans on capture volume by deviation mirror 120.Person under inspection in the visual field 135 is by eyes 134 expressions, and it illuminates by obtaining light source 110.
Eyes 134 in the visual field 135 are got back to rough deviation mirror 120 with the light retroeflection, rough deviation mirror 120 via mirror 119 and beam splitter 115 with photoconduction to camera 150.Camera 150 is the extensive angle cameras that are used to discern the general location of eyes 134.In one embodiment, camera 150 is electronic image sensors of CCD for example, and it periodically writes down the discrete picture of visual field 135.In one approach, the rapid serial of camera 150 document images is to monitor moving of visual field 135 interior objects 134.Analyzed with the identification eyes by software (for example, being included in the controller 190) from the signal of extensive angle camera, eyes are owing to the cause from the retroeflection of eyes 134 looks it is the round dot that becomes clear.Camera 150 is with the wavelength operation identical with light source 110.Can use the surround lighting on the wavelengths filters elimination backhaul optical path, pass through illumination wavelengths simultaneously.In addition, can carry out gating to light source 110.Camera 150 exposure and light source 110 gatings also can increase isolation between imaging and guiding (or wavefront sensor) camera synchronously.This also can reduce the influence of background light contamination synchronously.
In case discerned eyes 134, controller 190 just determines iris is carried out the plan of imaging.Preferably, capture the iris image (but needn't simultaneously) of two eyes so that increase the accuracy of identification.Among Fig. 2, iris 134A is carried out imaging.If necessary, controller 190 just guide rough deviation mirror 120 so that the eyes 134A that is paid close attention in the narrower visual field of imaging subsystems 200.Illustrate as Fig. 2, rough deviation mirror 120 also makes the wide visual field 135 that obtains subsystem 100 turn to, but does not need to do like this.Make and obtain the advantage that subsystem 100 and imaging subsystems 200 turn to together and be, kept wavefront sensor 227 and obtained fixed relationship between the camera 150.
In a kind of version, the use polarization is distinguished retroreflection light and the flash of light from objective eye 134.Make illumination light polarization, and beam splitter 215 is polarization beam splitters from WFS light source 210.The original light through polarization of beam splitter 215 reflections is with its guiding eyes 134.(for example be placed on beam splitter 215 rears, between beam splitter 215 and the lens 221) quarter wave plate at twice by (promptly, from WFS light source 210 once pass through when the eyes 134A transmission and during from eyes 134A retroeflection for the second time by) polarization is revolved turn 90 degrees.Flash of light (that is, from the reflection of smooth surface) keeps polarization of incident light usually and therefore will be reflected by polarization beam splitter 215 on return path, and will can not be delivered to wavefront sensor 227.These flashes of light can comprise from the reflection of object lens 221, from reflection of eyes 134 front portions or glass etc.Yet, do not keep polarization of incident light from the amphiblestroid retroeflection of objective eye 134 owing to the cause of eye structure, and therefore a part of transmission of this light is passed beam splitter and is arrived wavefront sensor 227.
Though adaptive optical element can be used in many application to proofread and correct the high order aberration, but in the case, the adaptive optics loop is mainly used in follows the tracks of (that is, proofreading and correct the tip/droop error in the wave front) fast and preferably also is used to carry out focus correction eyes 134A.This remains on iris 134A in the narrow visual field of camera 250, and camera is focused on (if implementing focus correction).In this example, light source 210 does not provide main illumination for camera 250.In fact, extra light source 248 (that is iris imaging light source) provides off-axis lighting to iris 134 for camera 250.For instance, can use the interior LED of near infrared wavelength region.(pigment melanin) is more transparent at the longer wavelength place for the protectiveness melanocyte.Therefore, have the light source of these wavelength, in the painted eyes of severe, be easier to see the details of iris structure by use.Perhaps, can use any other light source that meets safe level.Off-axis lighting produces higher contrast and less illusion usually.Also realize may be to the location of identification accuracy disadvantageous flash of light at the off-axis lighting angle.Also can be by using polarization illumination to reduce flash of light to iris camera 250 with polarization filter.In alternative method, can provide illumination by ambient lighting, visible or infrared flash or these combination to camera 250.
Traditional ADAPTIVE OPTICS SYSTEMS (for example those ADAPTIVE OPTICS SYSTEMS of developing for uranology) may be too greatly, too complicated and/or cost too high so that can not be used for for example application of iris imaging effectively.Yet, CA, the recent advances of the AOptix Technologies of Campbell has caused realizing the development less than the complete ADAPTIVE OPTICS SYSTEMS (comprising electronic component) of the size of footwear box.The AOptix ADAPTIVE OPTICS SYSTEMS need less than the power of 25W and can be under unserviced situation reliably operation continue than long duration.The small size of AOptix ADAPTIVE OPTICS SYSTEMS, weight and power and high reliability make it be suitable for the application that iris imaging for example described herein is used.
In the system that these compact, deformable mirror 220 is deformable curvature mirror, and therefore it cause distortion based on apply different voltages on the zones of different of piezoelectric.The application on January 25 calendar year 2001 of J.Elon Graves and Malcolm J.Northcott and the 6th, 464, No. 364 United States Patent (USP)s " Deformable CurvatureMirror " of issuing on October 15th, 2002; The application on January 25 calendar year 2001 of J.Elon Graves and Malcolm J.Northcott and the 6th, 568, No. 647 United States Patent (USP)s " Mounting Apparatus for Deformable Mirror " of issuing on May 27th, 2003; And the June 16 calendar year 2001 of J.Elon Graves and Malcolm J.Northcott application the 6th, the more details of describing and having showed the deformable mirror of this type in 721, No. 510 United States Patent (USP)s " Atmospheric Optical Data Transmission System ".In addition, wavefront sensor 227 is based on the wave front curvature sensor that defocuses pupil image.The application in 26 days Mays in 2000 of J.ElonGraves and Malcolm J.Northcott and the 6th, 452, No. 145 United States Patent (USP)s " Method and Apparatus for Wavefront Sensing " of issuing on September 17th, 2002; And the June 16 calendar year 2001 of J.Elon Graves and Malcolm J.Northcott application the 6th, the more details of describing and having showed the wave front curvature sensor of this type in 721, No. 510 United States Patent (USP)s " AtmosphericOptical Data Transmission System ".More than all patents all be incorporated herein by reference.
In one embodiment, the iris imaging system of Fig. 2 is through designing to be used for corridor, airport, customs inspection post, public transportation station, secure buildings hall etc.Reach at least 10 meters projection distance will realize to than the scanning in big room or corridor so that the passenger is discerned.For instance, a device can be placed near the departures on airport and/or the screen that enters the station.Therefore, described system can discern any people who attempts to read screen content.
In order to realize this particular design, obtain the visual field 135 that subsystem 100 has approximate 12 degree, thereby cause measuring the capture volume 50 of the approximate 2m * 2m in 10m scope place * 2m (no-raster).Obtaining light source 110 is that wavelength is at 750 light emitting diodes (LED) that arrive in the 980nm scope.Shorter wavelength provides sensor quantum efficienty preferably, is used for non-visible operation but need be longer than the wavelength that is similar to 890nm.Longer wavelength also is possible, but needs the detecting device of more expensive (non-silicon).Led light source is normally preferred.LASER Light Source is owing to eye-safe is considered to have problems, but can be used under the situation of careful manipulation.In some cases, but also using gases discharge lamp.Also can use for example thermal source of tungsten lamp and arc lamp, but described thermal source will efficient be lower owing to the cause that needs wavelength to filter.
In this particular design, obtain the illumination wavelengths that subsystem 100 uses and be different from the illumination wavelengths that imaging subsystems 200 uses, so mirror 119 can be wavelength selectivity, separating with light at the light that obtains subsystem 100 at imaging subsystems.Obtaining camera 150 is that resolution is the monochromatic TV camera of infrared enhancement mode of approximate 720 * 500 pixels.Camera 150 is operated with the 30Hz frame rate.
With respect to imaging subsystems 200, resolution requirement has promoted the design of iris imaging system 200.Consider the resolution requirement of 75 microns of every pixels.Suppose performance by diffraction limit, required aperture d is given by d=λ z/r, and wherein z is that projection distance and r are required resolution.For instance, suppose λ=0.82 μ m, and z=10m, required aperture is 11cm.As another example, can under visible wavelength 0.5 μ m, projection distance 10m and 5cm aperture by diffraction limit, realize the resolution of 100 μ m.Yet, owing to observe the contrast of enhancing at the longer wavelength place, so for iris imaging, infrared wavelength is normally preferred.
Resolution requirement by diffraction limit and large aperture also cause the limited depth of field.If because the several picture that the focal length depth of field causes diffusion is set at less than diffraction limit half, depth of field l is by l=r so
2/ λ is given.0.82 μ m example produces the depth of field of approximate 7mm.0.5 μ m example produces the depth of field of approximate 2cm.The depth of field of about several millimeters or several centimetres makes mobile object is focused on difficulty.Therefore, quick focus correction of enforcement and quick the tracking are favourable for the adaptive optics loop.The iris imaging system that utilizes adaptive optical element to promote, can be in several milliseconds of recognition objective photographic images.Therefore, use adaptive optical element can increase the speed and the accuracy of the image capture of the application that relates to noncooperative target.
Also can use other version and method to realize focus adjustment.For instance, can use lens of variable focal length or deformable mirror to focus.The use mobile and the variable refractive index element of electromechanical lens position adjustment, camera 250 is the alternative of focusing.In addition, the focus wavefront sensing can be measured and shake based on picture contrast, or passes through to use special focus wavefront sensor, or measures the distance of eyes by the flight time of using light pulse or acoustic impluse.
Continue above-mentioned particular instance, the WFS light source 210 that can select to use in the iris imaging system 200 illuminates eyes, makes target individual not can be appreciated that described process.The LED of wavelength in 750 to 980nm scopes normally preferred (and be used for non-visible operation greater than approximate 890nm), but can use other light source as mentioned above.It is favourable filling the telescopic aperture with illumination light shown in Figure 2, because this guarantees that pupil is illuminated fully by eye reflections.Preferably, iris imaging light source 248 also is LED.Near the current regulation of the iris imaging standard 850nm scope wavelength.
In this example, also select WFS illumination wavelengths (using) to be different from the illumination that is used for being undertaken imaging by 250 pairs of irises of camera by wavefront sensor 227.Therefore, beam splitter 225 is dichromatic to increase efficient.Yet the separation of these wavelength is not what need.Can use other technology to separate different light beams.For instance, can change into by iris imaging illumination timing separation and WFS illumination.WFS LED 210 can glimmer synchronously with WFS chopper (Fig. 2 is not shown), and when wavefront sensor 227 did not compile signal, iris imaging illumination 248 flickers were to fill the dead time.Iris imaging camera 250 is high-quality forming monochrome image device preferably.Because the cause that high speed is followed the tracks of, this imager 250 can have relative pixel than peanut, for example 640 * 480 video imaging devices of standard are comparatively convenient.For iris imaging camera 250, high-quality, high-quantum efficiency and low signal-to-noise ratio are compared relative more important with resolution.Obtain camera 150 and will have independent illuminator 110 usually.Disturb if obtain between illumination 110, iris imaging illumination 248 and/or the meticulous tracking illumination 210, can use various technology that isolation is provided so, including (for example) technology based on wavelength, polarization, time separation and/or angle or apart.
The example of Fig. 2 is based on the retroeflection from eyes.Fig. 3 is the explanation from the retroeflection of human eye.The inherent geometry of eyes impels it to serve as the retroeflection body.The light that enters eyepiece 304 focuses on the retina 314.Any light that is scattered back to lens 404 by retina turns back along the path that it leaves eyes.Because retina is the focal plane of eyepiece, so light is guided on the backscattering direction consumingly.As shown in Figure 3, light enters eyeball by pupil and from the back curvature surface reflection of retina 314.This just backreflection that takes place from retina 314 can be used for driving the meticulous tracker (for example, the wavefront sensor in the adaptive optics loop) the imaging subsystems.And the explanation display lighting of Fig. 3 need not from facing (face-on) orientation to produce retroeflection.Therefore, the person under inspection need not directly to stare the iris imaging camera so that obtain and imaging system work.
Fig. 4 is the explanation of the typical reflectance spectrum of human eye.This figure provides in the paper of the Niels Zagers of Univ Utrecht Netherlands.Reflectance shows is towards infrared strong peak value.Use the wavelength (CD reads optical maser wavelength) of 750nm, the expection reflectivity is 4% of white lambert's diffuser value.The backreflection characteristic is stronger in red and nearly IR (about 800nm) wavelength, because the melanocyte that occurs in the retina is less in red wavelength place absorbability.In 750nm or long wave strong point more, the person under inspection will only see faint illumination, because this is outside the nominal visibility region.In 880nm or long wave strong point more, light source will be invisible basically.
How following example demonstration can be used for the closed loop operation of ADAPTIVE OPTICS SYSTEMS from the retroreflection light of eyes 234.The power of available 0.1mW throws light on to the person under inspection's of 10m distance eyes, and the power of described 0.1mW is fully in the eye-safe limit.In this example, the expection retroreflection light is approximately 6.4 * 10
-13W/cm
2Suppose and use the 5cm imaging len to realize 100 microns resolution, then on wavefront sensor, capture approximate 1.2 * 10
-11W.This is corresponding to per second approximate 5 * 10
7The photon flux of individual photon.In one embodiment, use the low order ADAPTIVE OPTICS SYSTEMS of moving with relatively slow speed.For instance, the each renewal of the every actuator of 19 actuator ADAPTIVE OPTICS SYSTEMS of upgrading with 1KHz provides approximate 2500 photons.Having the CCD type detecting device that is better than 50 electron read noise and 50% quantum efficiency will provide enough signal to noise ratio (S/N ratio) to carry out the closed loop operation of ADAPTIVE OPTICS SYSTEMS.Relatively, by convention, realize being better than 10 electron read noise and 90% quantum efficiency at the scientific grade CCD imaging.Therefore, can use retroreflection light to obtain meticulous tracking and the imaging of feedback signal to support that adaptive optical element is auxiliary.
Use eyes to comprise low-cost and long distance with the advantage that drives wavefront sensor as the retroeflection body.Low-cost owing to using cheap silicon detecting device as wavefront sensor and cheap LED ability as light source.Because the stronger cause of directivity of retroeflection, even also realize enough signals in long distance.Yet the retina retroeflection is not rendered as point source, therefore uses higher dynamic range detectors to produce wavefront signal accurately.
In the example of Fig. 2, are retina retroeflection from the reflection of eyes.Perhaps, the front surface of eyes serves as reflectivity and is about 4% partially reflecting mirror (partial mirror).Come since then reflecting to form of surface to replace the flash of light that imaging subsystems 200 is turned to of can be used for of retroeflection.For instance, the system of Fig. 2 can be through revising so that light source 210 illuminates eyes 134A, but wavefront sensor 227 is driven by flash of light reflection rather than retroeflection from eyes.Because flash of light can produce by off-axis lighting, so light source 210 is movable to outer or even telescope 221 outsides of imaging subsystems 200 of axle.In the example of Fig. 5, light source 210 is replaced by external light source 212.This light source 212 is positioned at the position of nearly approximate working flare 248, but still produces the flash of light at telescope 221.In addition, flash of light looks the image that dwindles that looks like light source, so its picture point source more often.The advantage that is produced is that the size and dimension of flash of light is not the majorant apart from person under inspection's distance.
An advantage that drives wavefront sensor with the flash of light of eyeball is, do not have restriction on the distance that can use from the flash of light of eyeball.And the light source of similarity does not need to have the wavefront sensor of high dynamic range.Yet, to compare with retroeflection from eyes, less light is passed in flash of light back, therefore may need wavefront sensor sensitivity higher or illumination flux is higher.
Although embodiment contains many details, these details should not be construed as and limit the scope of the invention, but only should be interpreted as illustrating different instances of the present invention and aspect.Should be appreciated that scope of the present invention comprises other embodiment that does not above discuss in detail.Can be under the situation that does not break away from the spirit and scope of the present invention that define in the appended claims, configuration, operation and the details of the method and apparatus of the present invention that this paper is disclosed are made various other modifications, variation and the transformation that is understood by those skilled in the art that.For instance, the meticulous tracker in the imaging subsystems can use deformable mirror that camera is turned between eyes, but deformable mirror can be by being not that feedback from wavefront sensor drives.For instance, can use laser radar, radar and other ranging technology, image parallactic or picture contrast measurement and pattern recognition to drive deformable mirror.Therefore, scope of the present invention should be determined by appended claims and legal equivalents thereof.
Claims (47)
1. iris imaging system that comprises imaging subsystems, described imaging subsystems comprises:
Camera, it is used to capture the iris image with the enough resolution that is used for bio-identification;
Light source, it is used to produce the light that illuminates eyes; And
Meticulous tracker, it is used for making described camera turn to eyes based on the eye reflections of the light that illuminates eyes.
2. iris imaging according to claim 1 system, wherein said eye reflections comprises the retroeflection from eyes.
3. iris imaging according to claim 1 system, wherein said eye reflections comprise the flash of light reflection from eyes.
4. iris imaging according to claim 1 system, wherein said meticulous tracker comprises the adaptive optics loop based on described eye reflections light.
5. iris imaging according to claim 4 system, wherein said adaptive optics loop comprises:
Deformable mirror, it is used to make described camera to turn to the wave front of eyes and the described eye reflections light of adjusting;
Wavefront sensor, it is used for the wave front of the described eye reflections light of sensing; And
Controller, it is coupling between described deformable mirror and the described wavefront sensor, is used for regulating described deformable mirror based on the described wave front that senses.
6. iris imaging according to claim 5 system, wherein said deformable mirror also makes described camera focus on.
7. iris imaging according to claim 5 system, wherein said imaging subsystems further comprises:
Polarization beam splitter, it is positioned between described deformable mirror and the described wavefront sensor, wherein said light source produces polarized light and described polarization beam splitter will enter the described polarized light and the combination of described deformable mirror of optical path, but described wavefront sensor is left in the back light reflection of identical polarization.
8. iris imaging according to claim 5 system, wherein said deformable mirror is based on the deformable curvature mirror that applies different voltages on the zones of different of piezoelectric.
9. iris imaging according to claim 5 system, wherein said wavefront sensor is based on the wave front curvature sensor that defocuses pupil image.
10. iris imaging according to claim 4 system, wherein said adaptive optics loop also makes described camera focus on.
11. comprising, iris imaging according to claim 1 system, wherein said meticulous tracker be used to make described camera to turn to the deformable mirror of eyes.
12. having per second, iris imaging according to claim 1 system, wherein said meticulous tracker capture speed with at least 10 irises of imaging.
13. can being higher than the accuracy of 0.5cm, iris imaging according to claim 1 system, wherein said meticulous tracker follow the tracks of iris.
14. iris imaging according to claim 1 system, wherein said light source produces the light of non-laser.
15. iris imaging according to claim 1 system, wherein said light source is LED.
16. iris imaging according to claim 1 system, wherein said light source produces greater than the light in the wavelength coverage of 750nm.
17. iris imaging according to claim 1 system, wherein said light source produces 750nm to the interior light of 980nm wavelength coverage.
18. iris imaging according to claim 1 system, wherein said light source produces greater than the light in the wavelength coverage of 850nm.
19. iris imaging according to claim 1 system, wherein said light source produces the light in the human nonvisible wavelength scope.
20. iris imaging according to claim 1 system, wherein said camera is a monochrome cameras.
21. iris imaging according to claim 1 system, wherein said camera is captured has 200 microns or more high-resolution iris image.
22. iris imaging according to claim 1 system, wherein said camera is captured has 100 microns or more high-resolution iris image.
23. iris imaging according to claim 1 system, wherein said camera is captured has 75 microns or more high-resolution iris image.
24. iris imaging according to claim 1 system, it further comprises:
The outer light source of axle, it is used for described iris is thrown light on so that carry out image capture by described camera.
25. iris imaging according to claim 1 system, wherein said imaging subsystems can cover at least 1 cubic metre capture volume.
26. iris imaging according to claim 1 system, wherein said camera can be captured iris image at the projection distance place of 5m at least.
27. iris imaging according to claim 1 system, wherein said camera can be captured iris image at the projection distance place of 10m at least.
28. iris imaging according to claim 1 system, it further comprises:
Obtain subsystem, it is used to discern the apparent position of person under inspection in the capture volume; And
Controller, it is coupled to described subsystem and the described imaging subsystems of obtaining, and is used to coordinate described two subsystems.
29. iris imaging according to claim 28 system wherein saidly obtains the described apparent position that eye reflections that subsystem takes place from described person under inspection's eyes based on illumination light is discerned the person under inspection.
30. iris imaging according to claim 28 system, the wherein said subsystem that obtains is stared described whole capture volume.
31. iris imaging according to claim 28 system, the wherein said subsystem that obtains is in the enterprising line scanning of described capture volume.
32. iris imaging according to claim 28 system, wherein said subsystem and the described imaging subsystems of obtaining is along common optical axis alignment.
33. the iris to eyes carries out imaging method, it comprises:
Use up and illuminate eyes;
Make camera turn to eyes based on described illumination light from the eye reflections of eyes; And
Described camera is captured the iris image with the enough resolution that is used for bio-identification.
34. method according to claim 33, wherein said eye reflections comprises the retroeflection from eyes.
35. method according to claim 33, wherein said eye reflections comprise the flash of light reflection from eyes.
36. method according to claim 33, the wherein said step that makes described camera turn to eyes comprise that use makes described camera turn to eyes based on the adaptive optics loop of described eye reflections light.
37. method according to claim 33, it further comprises:
Based on described eye reflections light described camera is focused on the eyes.
38. method according to claim 33, the wherein said step that makes described camera turn to eyes can make described camera per second turn at least 10 eyes.
39. comprising, method according to claim 33, the wherein said step that illuminates eyes use greater than the bright eyes of the illumination in the 750nm wavelength coverage.
40. method according to claim 33, the wherein said step that illuminates eyes comprise with the bright eyes of illumination in the human nonvisible wavelength scope.
41. capturing, method according to claim 33, wherein said camera have 200 microns or more high-resolution iris image.
42. method according to claim 33 wherein can make described camera turn to capture volume to cover at least 1 cubic metre.
43. method according to claim 33, wherein said camera can be captured iris image at the projection distance place of 10m at least.
44. method according to claim 33, it further comprises:
Person under inspection's apparent position in the identification capture volume; The wherein said step that makes described camera turn to eyes is based in part on the apparent position of described identification.
45. according to the described method of claim 44, the eye reflections that the step of wherein said identification person under inspection's described apparent position takes place from described person under inspection's eyes based on illumination light.
46. according to the described method of claim 44, the step of wherein said identification person under inspection's described apparent position comprises stares described whole capture volume.
47. according to the described method of claim 44, the step of wherein said identification person under inspection's described apparent position is included in the enterprising line scanning of described capture volume.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US63433104P | 2004-12-07 | 2004-12-07 | |
| US60/634,331 | 2004-12-07 | ||
| US60/654,638 | 2005-02-17 |
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| Publication Number | Publication Date |
|---|---|
| CN101099164A true CN101099164A (en) | 2008-01-02 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA2005800460413A Pending CN101099164A (en) | 2004-12-07 | 2005-12-07 | Post processing of iris images to increase image quality |
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| CN (1) | CN101099164A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103961055A (en) * | 2013-06-20 | 2014-08-06 | 深圳市斯尔顿科技有限公司 | Optical system and optical method for measuring human eye white-to-white distance |
| CN105988586A (en) * | 2015-03-17 | 2016-10-05 | 摩托罗拉移动有限责任公司 | Low-power iris authentication alignment |
| CN106062776A (en) * | 2014-02-26 | 2016-10-26 | 微软技术许可有限责任公司 | Polarized gaze tracking |
| CN106796655A (en) * | 2014-09-12 | 2017-05-31 | 眼锁有限责任公司 | Method and apparatus for guiding sight line of the user in iris authentication system |
| CN107847130A (en) * | 2015-07-17 | 2018-03-27 | 索尼公司 | Eyeball observation device, glasses type terminal, method for detecting sight line and program |
| CN110300976A (en) * | 2017-02-17 | 2019-10-01 | 亚德诺半导体无限责任公司 | Eye gaze tracking |
| CN113242710A (en) * | 2018-12-20 | 2021-08-10 | 依视路国际公司 | Method and apparatus for determining a refractive characteristic of an eye of a subject |
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2005
- 2005-12-07 CN CNA2005800460413A patent/CN101099164A/en active Pending
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103961055A (en) * | 2013-06-20 | 2014-08-06 | 深圳市斯尔顿科技有限公司 | Optical system and optical method for measuring human eye white-to-white distance |
| CN103961055B (en) * | 2013-06-20 | 2015-07-22 | 深圳市斯尔顿科技有限公司 | Optical system and optical method for measuring human eye white-to-white distance |
| CN106062776A (en) * | 2014-02-26 | 2016-10-26 | 微软技术许可有限责任公司 | Polarized gaze tracking |
| CN106062776B (en) * | 2014-02-26 | 2019-04-30 | 微软技术许可有限责任公司 | The eye tracking of polarization |
| CN106796655A (en) * | 2014-09-12 | 2017-05-31 | 眼锁有限责任公司 | Method and apparatus for guiding sight line of the user in iris authentication system |
| CN105988586A (en) * | 2015-03-17 | 2016-10-05 | 摩托罗拉移动有限责任公司 | Low-power iris authentication alignment |
| CN107847130A (en) * | 2015-07-17 | 2018-03-27 | 索尼公司 | Eyeball observation device, glasses type terminal, method for detecting sight line and program |
| CN110300976A (en) * | 2017-02-17 | 2019-10-01 | 亚德诺半导体无限责任公司 | Eye gaze tracking |
| CN110300976B (en) * | 2017-02-17 | 2024-01-05 | 亚德诺半导体国际无限责任公司 | Eye gaze tracking |
| CN113242710A (en) * | 2018-12-20 | 2021-08-10 | 依视路国际公司 | Method and apparatus for determining a refractive characteristic of an eye of a subject |
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