Optics: measuring and testing – Document pattern analysis or verification
Patent
1995-01-12
1997-04-15
Gonzalez, Frank
Optics: measuring and testing
Document pattern analysis or verification
382124, 382125, 382126, 382127, G06K 974
Patent
active
056215169
ABSTRACT:
An optical device for forming an image of an uneven surface, including a plane-parallel plate with a pair of parallel plane surfaces which is made of a transparent material having a refractive index larger than that of water and transparent to illuminating light. An uneven object (object having an uneven surface) is placed in close contact with one plane surface of the plane-parallel plate. A light source illuminates the uneven object through the plane-parallel plate. Among light rays scattered back into the plane-parallel plate by the uneven object and totally reflected at the other plane surface of the plane-parallel plate, only light that is totally reflected at an angle larger than the critical angle at the boundary between the plane-parallel plate and water is taken in by an image-forming device.
REFERENCES:
patent: 4681435 (1987-07-01), Kubota et al.
patent: 4924085 (1990-05-01), Kato et al.
patent: 5088817 (1992-02-01), Igaki et al.
patent: 5416573 (1995-05-01), Sartor, Jr.
Fujitsu Scientific and Tec. J., vol. 25, No. 4, 1989 Kawasaki, JP, pp. 287-296, XP 000103957 T. Shinzaki et al. "Holographic Fingerprint Sensor", Section 4.3 Optimizing the lighting angle *Figures 10-12*.
Iwata Satoshi
Shinzaki Takashi
Eisenberg Jason D.
Fujitsu Limited
Gonzalez Frank
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