Mapping of Blood Vessels for Biometric Authentication
First Claim
1. Apparatus for thermoacoustic imaging, the apparatus comprising:
- a microwave source configured to provide a microwave output;
an microwave emitter array including two or more unit cells, wherein the unit cells each comprise two or more near-field excitation elements;
wherein the microwave emitter array is configured to receive the microwave output from the microwave source, and wherein the microwave emitter array is configured to provide microwave excitation to a target via the near-field excitation elements of the unit cells;
wherein the microwave output is provided to the near-field excitation elements of the unit cells with relative phases selected to provide polarization eccentricity of 0.87 or less within the target;
an acoustic sensor array having one or more sensor elements configured to receive acoustic signals from the target responsive to the microwave excitation;
a processor configured to receive signals from the acoustic sensor array and to provide an acoustic image of the target.
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Abstract
Improved thermoacoustic imaging is provided by ensuring directional uniformity of the microwave excitation provided to the target being imaged. This directional uniformity can be quantified in terms of the eccentricity e of the polarization ellipse of the microwave excitation. We have e≦0.87, preferably e≦0.71, and more preferably e≦0.32. Optical excitation can be provided in addition to the microwave excitation. Excitation can be performed at multiple optical wavelengths and/or microwave frequencies to improve depth uniformity. In addition, the employment of excitation cells with optimized spacing and geometry provides the uniformity in another two degrees of freedom. One potential application is to detect blood vessel in user'"'"'s finger for biometric authentication.
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Citations
25 Claims
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1. Apparatus for thermoacoustic imaging, the apparatus comprising:
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a microwave source configured to provide a microwave output; an microwave emitter array including two or more unit cells, wherein the unit cells each comprise two or more near-field excitation elements; wherein the microwave emitter array is configured to receive the microwave output from the microwave source, and wherein the microwave emitter array is configured to provide microwave excitation to a target via the near-field excitation elements of the unit cells; wherein the microwave output is provided to the near-field excitation elements of the unit cells with relative phases selected to provide polarization eccentricity of 0.87 or less within the target; an acoustic sensor array having one or more sensor elements configured to receive acoustic signals from the target responsive to the microwave excitation; a processor configured to receive signals from the acoustic sensor array and to provide an acoustic image of the target. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification