Abstract:
This invention relates to the use of holographic optical elements in the design and application of biometric scanning instruments used typically for capturing biometric information such as fingerprints and handprints. A system and method for capturing print images from select areas of a platen are presented. The system includes a reference beam source that provides a reference beam, holographic material that receives the reference beam, a platen on a surface of the holographic material that receives a biometric object, and an image sensor. Variations in orientation of the reference beam cause differing areas of the platen to be mapped onto the image sensor, thereby obtaining both different image translations and magnifications of at least a portion of the biometric object.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims benefit to U.S. Provisional Pat. Appl. No. 60/603,282, filed Aug. 23, 2004, the disclosure of which is hereby incorporated by reference herein in its entirety. 

   BRIEF SUMMARY OF THE INVENTION 
   This invention relates to the use of holographic optical elements in the design and application of biometric scanning instruments used typically for capturing biometric information such as fingerprints and handprints. Holographic optical elements can be used in place of conventional print scanning elements, such as platens and prisms, to provide the opportunity for print scanning manufacturers to reduce product development cycle times, reduce product cost, size, and weight, and provide optical design flexibility not afforded by common glass and plastic refractive optical elements. 
   A system and method for capturing print images from select areas of a platen are presented. The system includes a reference beam source that provides a reference beam, holographic material that receives the reference beam, a platen on a surface of the holographic material that receives a biometric object, and an image sensor. Variations in orientation of the reference beam cause differing areas of the holographic platen to be mapped onto the image sensor, thereby obtaining both different image translations (i.e., images mapping to differing portions of the image sensor) and magnifications of at least a portion of the biometric object. 
   Further embodiments, features, and advantages of the present invention, as well as the structure and operation of the various embodiments of the present invention, are described in detail below with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
     The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. 
       FIG. 1  depicts a holographic imaging system, according to an embodiment of the present invention. 
       FIG. 2  depicts a holographic imaging system using multiple reference beams, according to an embodiment of the present invention. 
       FIG. 3  is a flowchart depicting a method for capturing print images from select areas of a platen, according to an embodiment of the present invention. 
   

   The present invention will be described with reference to the accompanying drawings. The drawing in which an element first appears is typically indicated by the leftmost digit(s) in the corresponding reference number. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Holographic technologies can be used to realize a number of different devices, such as holographic secure optical keying devices, holographic portable personalized identification devices, non-contact optical doppler biometric scanners, etc. Holographic material is used in biometric scanners, such as live print scanners, to capture biometric data and to provide additional operational features. Holographic material can be any type of holographic material or element, including but not limited to one or more holographic optical elements, holographic diffraction grating(s), holographic filter(s), holographic diffractive optic(s), or combinations thereof. An example holographic optical element may include, but is not limited to, a volume holographic optical element. 
   Holographic material can be configured to act as one or more optical components, such as a lens and/or mirror, at various angles of input light. In this way, holographic material can shape and direct incident reference beams to capture desired images including print images as described herein. At least one reference beam is required to be used with holographic material. In some applications, output from a coherent light source (such as a laser, for example) is separated into two or more beams for illumination and reference beam purposes. Alternatively, the reference beam may be used to illuminate the object. When holographic material is illuminated by a reference beam, a high contrast print image can be obtained. Typically, a print image will be due to frustrated total internal reflection (“TIR”) caused by a reference beam at a platen surface of the holographic material in the presence of print ridges or valleys. 
   The present invention includes using various reference beams with holographic material used as a platen of a biometric print scanner, such as a biometric fingerprint or handprint scanner, for example. This operational feature of using holographic material as a platen can also be utilized in other types of instruments where platens are required. 
   While specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the pertinent art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the present invention. It will be apparent to a person skilled in the pertinent art that this invention can also be employed in a variety of other applications. 
     FIG. 1  depicts a holographic imaging system  100 , according to an embodiment of the present invention. Holographic imaging system  100  includes holographic material  110  having a platen  102 , a reference beam source  104  that provides reference beam  105 , and an image sensor  106 . Platen  102  can be a surface of holographic material  110  or is at least optically coupled to the holographic material  110 . A biometric object  107 , such as a finger or hand, for example, is placed onto platen  102 . Holographic material  110  is configured to shape, focus, and/or direct light. In particular, holographic material  110  acts to direct light from reference beam  105  to platen  102 . When a reference beam  105  is provided by reference beam source  104  to holographic material  110 , an image of at least a portion of platen  102 , containing an image of at least a portion of biometric object  107 , is received at image sensor  106 . 
     FIG. 2  depicts a holographic imaging system, such as that shown in  FIG. 1 , for example, using various orientations of a reference beam, according to an embodiment of the present invention. Holographic material  110  is configured in such a way that different orientations of the reference beam allow for different image translations and/or magnifications. 
   In  FIG. 2 , the configured holographic material  110 , when illuminated by various reference beams  208 ,  212 ,  216 , and  220  at appropriate respective orientations, causes varying imaged platen areas  210 ,  214 ,  218 , and  222  to be mapped onto the image sensor. Each of these imaged platen areas is mapped from a different location on platen  102 . Each location can be of a different size. The images from these differing locations on the platen represent different image translations. In this way, when a biometric object  107  is placed on platen  102 , a different portion of biometric object  107  can be imaged at image sensor  106 , depending on the orientation of the reference beam. 
   Depending on the particular image translation and system characteristics (e.g., the arrangement and geometry of the image sensor relative to the platen area), the magnification of the image can also be changed. In other words, the configuration of the holographic material  110  and system characteristics can also determine a magnification of the resulting image. 
   The above description discusses the detection of different image translations and magnifications. In additional embodiments, however, one or more image translations only can be detected, one or more magnifications only can be detected, or one or more combinations thereof can be detected. 
   The image translation and magnification features allow a large platen area and a small platen area to be imaged at different resolutions with the same system. For example, a large area (such as that shown in imaged platen area  210  of example (a) of  FIG. 2 , for example) can be imaged at a reduced image resolution. The system can then be switched to a smaller region of interest (such as that shown in imaged platen area  214  of example (b) of  FIG. 2 , for example) and imaged at a higher, or increased, image resolution. 
   Alternative relationships between various orientations of the reference beams  208 ,  212 ,  216 , and  220  are shown in examples (a) through (n) of  FIG. 2 . There are no implied relationships between the various reference beams. As would be understood by a person skilled in the relevant arts, the distance between the image and the holographic material can vary as designed. 
     FIG. 3  is a flowchart depicting a method  300  of capturing print images from select areas of a platen, corresponding to embodiments of the present invention shown in  FIGS. 1 and 2 . Method  300  begins at step  302  and immediately proceeds to step  304 . In step  304 , a biometric object, such as a hand or finger, for example, is placed onto a platen surface of a holographic material. In step  306 , a reference beam is provided to the holographic material. In step  308 , an image of a select area of the platen is received at an image sensor. In step  310 , the reference beam is reoriented. In step  312 , an additional image of an additional select area of the platen is received at the image sensor. In step  314 , steps  310  and  312  are repeated until all desired select areas of the platen have been imaged. The resolution of the resulting images can be of differing resolutions, depending on the size of the platen areas imaged. Method  300  terminates at step  316 . 
   Method  300  can be fully or partially automated. For example, a controller (not shown) can send control signals to indicate to a user to place his or her hand in step  304 . As another example, the controller can send control signals to a reference beam source to provide a reference beam in step  306 . The controller can also send control signals to a reference beam source to reorient the reference beam in step  310 . Additionally, the controller can also send control signals to the image sensor to detect an image at steps  308 ,  312 , and  314 , as needed. 
   While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.