US2007035718A1PendingUtilityA1

Non-contact optical imaging system for biometric identification

39
Individually held — no corporate assignee on recordPriority: Aug 30, 2002Filed: Feb 3, 2005Published: Feb 15, 2007
Est. expiryAug 30, 2022(expired)· nominal 20-yr term from priority
Inventors:Waleed Sami Haddad
G06V 40/1312
39
PatentIndex Score
0
Cited by
0
References
0
Claims

Abstract

An optical system for imaging the features, ridges, and height variations of an object by exploiting the properties of specular reflection of light to maximize the contrast of the features, ridges, and height variations. The system provides a non-contact method of imaging objects suitable for biometric identification, such as the imaging of fingerprints. The system obtains the strong specular reflection using a properly shaped wave front. Optionally, the system can include a polarizer that filters and thereby enhances the specular reflection from the surface. Optionally, the system can also include pre-processing means for adjusting image brightness, contrast, and magnification.

Claims

exact text as granted — not AI-modified
1 . An optical system for imaging the features, ridges, and height variations of an object by exploiting the properties of specular reflection of light directly from an object to be imaged to maximize the contrast of the features, ridges, and height variations, the system comprising: 
 a. a light source;    b. a means for positioning the object to be imaged;    c. a means for shaping the wave front of the light emitted from the light source so as to cause it to illuminate the object so as to produce a strong specular reflection directly from an object to be imaged;    d. a means for focusing an image of the object using the reflected light; and    e. an image sensor positioned so that the light reflected from the object creates the image on it.    
     
     
         2 . An optical system for imaging the features, ridges, and height variations of an object by exploiting the properties of specular reflection of light directly from an object to be imaged to maximize the contrast of the features, ridges, and height variations, the system comprising: 
 a. a light source;    b. a means for verifying the position of the object to be imaged;    c. a means for shaping the wave front of the light emitted from the light source so as to cause it to illuminate the object so as to produce a strong specular reflection directly from an object to be imaged;    d. a means for focusing an image of the object using the reflected light; and    e. an image sensor positioned so that the light reflected from the object creates the image on it.    
     
     
         3 . An optical system for imaging the features, ridges, and height variations of an object by exploiting the properties of specular reflection of light directly from an object to be imaged to maximize the contrast of the features, ridges, and height variations, the system comprising: 
 a. a light source that emits a shaped wave front of light so as to cause it to illuminate the object so as to produce a strong specular reflection directly from an object to be imaged;    b. a means for positioning the object to be imaged;    c. a means for focusing an image of the object using the reflected light; and    d. an image sensor positioned so that the light reflected from the object creates the image on it.    
     
     
         4 . An optical system for imaging the features, ridges, and height variations of an object by exploiting the properties of specular reflection of light directly from an object to be imaged to maximize the contrast of the features, ridges, and height variations, the system comprising: 
 a. a light source that emits a shaped wave front of light so as to cause it to illuminate the object so as to produce a strong specular reflection directly from an object to be imaged;    b. a means for verifying the position of the object to be imaged;    c. a means for focusing an image of the object using the reflected light; and    d. an image sensor positioned so that the light reflected from the object creates the image on it.    
     
     
         5 . The optical system of  claim 1  or  2 , wherein the means for shaping the wave front of the illuminating light is a concave mirror.  
     
     
         6 . The optical system of  claim 5 , wherein the concave mirror is spherical.  
     
     
         7 . The optical system of  claim 1  or  2 , wherein the means for shaping the wave front of the illuminating light is a lens.  
     
     
         8 . The optical system of  claim 1  or  2 , wherein the means for shaping the wave front of the illuminating light is a holographic optical element (HOE).  
     
     
         9 . The optical system of  claim 3  or  4 , wherein the light source further comprises an array of individual light emitters arranged to shape the wave front illuminating the object.  
     
     
         10 . The optical system of  claim 1  or  3 , wherein the means for positioning the object is a rest.  
     
     
         11 . The optical system of  claim 2  or  4 , wherein the means for verifying the position of the object is a photoelectric detector.  
     
     
         12 . The optical system of  claim 1  or  3 , further comprising: 
 a. means for positioning the object so that the light illuminating the object hits it at an angle sufficient to partially linearly polarize the specular component of the reflected light and    b. a polarization filter positioned in the light beam reflected from the object and oriented so as to pass only the s-component of the polarized light to the image sensor.    
     
     
         13 . The optical system of  claim 2  or  4 , further comprising: 
 a. means for verifying that the position of the object is such that the light illuminating the object hits it at an angle sufficient to partially linearly polarize the specular component of the reflected light and    b. a polarization filter positioned in the light beam reflected from the object and oriented so as to pass only the s-component of the polarized light to the image sensor.    
     
     
         14 . The optical system of  claim 1 ,  2 ,  3 , or  4 , further comprising a first polarization filter placed between the light source and the object.  
     
     
         15 . The optical system of  claim 14 , further comprising a second polarization filter placed between the object and the image sensor positioned so that the light reflected off of the object passes through it and then to the image sensor and the second polarization filter, which is chosen and oriented to maximize the passing of the specular component of the reflected light.  
     
     
         16 . The optical system of  claim 15 , wherein the polarization filters are each comprised of polarizers only.  
     
     
         17 . The optical system of  claim 15 , wherein the polarization filters are each comprised of wave plates only.  
     
     
         18 . The optical system of  claim 15 , wherein the polarization filters are each comprised of a polarizer and a wave plate combined.  
     
     
         19 . The optical system of  claim 15 , wherein the second polarization filter is a linear filter.  
     
     
         20 . The optical system of  claim 14 , wherein the first polarization filter is a linear filter.  
     
     
         21 . The optical system of  claim 1 ,  2 ,  3 , or  4 , wherein the means for focusing the image is a lens positioned between the object and the image sensor to focus the light onto the image sensor.  
     
     
         22 . The optical system of  claim 1 ,  2 ,  3 , or  4 , wherein the light source is a light emitting diode or LED.  
     
     
         23 . The optical system of  claim 22 , wherein the light emitting diode or LED does not have a lens.  
     
     
         24 . The optical system of  claim 1 ,  2 ,  3 , or  4 , further comprising a spatial filter comprising: 
 a. a first stage with an aperture positioned against the light source for defining the effective size of the light source and    b. a second stage with an aperture positioned concentric to the aperture of the first stage for defining the angle of the cone of light emitted from the light source.    
     
     
         25 . The optical system of  claim 24 , wherein the shaping means is a mirror that is positioned in the light emitted from the light source through the spatial filter so as to capture the full cone of light.  
     
     
         26 . The optical system of  claim 1  or  3 , wherein the object is positioned so that the incident light is reflected from the object at an angle.  
     
     
         27 . The optical system of  claim 26 , wherein the object is positioned so that the incident light is reflected from the object at an angle that is close to Brewster's angle, thereby causing the specular component of the light to be partially polarized.  
     
     
         28 . The optical system of  claim 1  or  3 , wherein the object is positioned so that the light from the mirror is reflected from the object at about a 45° angle.  
     
     
         29 . The optical system of  claim 1  or  3 , 
 a. wherein the means for shaping the wave front of the illuminating light is a concave mirror and    b. wherein the object is positioned so as to fully illuminated the surface of the object being imaged in the cone of light reflected from the mirror.    
     
     
         30 . The optical system of  claim 29 , wherein the object is further positioned so that the focal point is collocated with the light source and further located so as to be outside of the cone of light emitted from the spatial filter.  
     
     
         31 . The optical system of  claim 30 , wherein the mirror is spherical.  
     
     
         32 . The optical system of  claim 1 ,  2 ,  3 , or  4 , wherein the means for focusing the image is a lens positioned between the object and the image sensor for focusing the image onto the image sensor.  
     
     
         33 . The optical system of  claim 32 , further comprising a small aperture stop positioned so that the light from the lens passes through it for obtaining a large depth of field.  
     
     
         34 . The optical system of  claim 26 , wherein the image sensor is tilted at an angle relative to the axis between the object and the image sensor so as to correct for the distortion of the image caused by the angle of the object to the same axis.  
     
     
         35 . The optical system of  claim 28 , wherein the image sensor is tilted at an angle of about 30°.  
     
     
         36 . The optical system of  claim 1 ,  2 ,  3 , or  4 , further comprising a means for processing the image to flatten it by normalizing the image brightness.  
     
     
         37 . The optical system of  claim 1 ,  2 ,  3 , or  4 , further comprising a means for non-linear processing of the image to enhance and normalize the contrast of the image.  
     
     
         38 . The optical system of  claim 1 ,  2 ,  3 , or  4 , further comprising a means for normalizing the magnification of the image.  
     
     
         39 . The optical system of  claim 1 ,  2 ,  3 , or  4  further comprising a polarization filter placed between the object and the image sensor positioned so that the light reflected off of the object passes through it and then to the image sensor and the polarization filter, which is chosen and oriented to maximize the passing of the specular component of the reflected light.  
     
     
         40 . The optical system of  claim 39 , further comprising a second polarization filter placed between the light source and the object.  
     
     
         41 . The optical system of  claim 2  or  4 , wherein the object's position is verified so that the incident light is reflected from the object at an angle.  
     
     
         42 . The optical system of  claim 41 , wherein the object's position is verified so that the incident light is reflected from the object at an angle that is close to Brewster's angle, thereby causing the specular component of the light to be partially polarized.  
     
     
         43 . The optical system of  2  or  4  wherein: 
 a. the means for shaping the wave front of the illuminating light is a concave mirror; and    b. the object's position is verified so that the light from the mirror is reflected from the object at about a 45° angle.    
     
     
         44 . The optical system of  claim 2  or  4  wherein, 
 a. the means for shaping the wave front of the illuminating light is a concave mirror; and    b. the object's position is verified so as to fully illuminate the surface of the object being imaged in the cone of light reflected from the mirror.    
     
     
         45 . The optical system of  claim 2  or  4 , wherein: 
 a. the means for shaping the wave front of the illuminating light is a concave mirror; and    b. the object is position is verified so that the light from the mirror is reflected from the object at about a 45° angle.    
     
     
         46 . The optical system of  claim 2  or  4  wherein: 
 a. the means for shaping the wave front of the illuminating light is a concave mirror; and    b. the object's position is verified so as to fully illuminated the surface of the object being imaged in the cone of light reflected from the mirror.    
     
     
         47 . The optical system of  claim 46 , wherein the optical geometry is such that the concave mirror forms an image of the light source and that image is located side by side the light source itself.  
     
     
         48 . The optical system of  claim 30 , wherein the image of the light source is located outside the cone of light emitted from the spatial filter.  
     
     
         49 . The optical system of  claim 24  wherein: 
 a. the means for shaping the wave front of the illuminating light is a concave mirror; and    b. the object is positioned so as to fully illuminated the surface of the object being imaged in the cone of light reflected from the mirror.

Join the waitlist — get patent alerts

Track US2007035718A1 — get alerts on status changes and closely related new filings.

We store only your email — no account needed. See our privacy policy.