| 摘要 |
PCT No. PCT/EP94/01194 Sec. 371 Date Dec. 29, 1994 Sec. 102(e) Date Dec. 29, 1994 PCT Filed Apr. 18, 1994 PCT Pub. No. WO94/24937 PCT Pub. Date Nov. 10, 1994A device for identifying fingerprints by use of ultrasound having an electronic evaluating circuit, a hollow cylinder of length L with a cover and a base plate, wherein the ultrasonic speed through the liquid equals c' and the cover is made from a material with ultrasonic speed c''. The outer side of the cover is planar to serve as a supporting surface for the fingerprint. The inner side is either convex (c'>c') or concave (c'<c'') with a spherical radius R and the condition L=R/|(c''/c')-1| must be satisfied. The individual ultrasonic receiver is arranged in the center of the base plate and extends over the smallest possible surface area. At least one annular transmitter is arranged concentrically around the individual ultrasonic receiver.
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