Measuring and testing – Dynamometers – Responsive to force
Reexamination Certificate
1998-11-19
2001-05-22
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to force
C073S862520
Reexamination Certificate
active
06234031
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a fingerprint detection apparatus which reads and converts a finger print into an electric signal and outputs the electric signal, and more particularly to a fingerprint detection apparatus which reads a fingerprint pattern based on a pressure distribution obtained when a finger is pressed against the fingerprint detection apparatus.
2. Description of the Related Art
As the information-oriented society and card-dependent society has develop rapidly, the strong demand for security is increasing. In order to satisfy this demand, progress is being made in development of various techniques which use a characteristic of the body of an individual to identify the individual. A technique for identifying individuals which uses a fingerprint and can be carried out readily is expected to have high applicability in the future for various terminal equipments and is expected to be put into practical use.
Most of the fingerprint detection apparatus which have been practical and widely used rely upon an optical system which employs a rectangular prism, as disclosed, for example, in Japanese Patent Laid-Open No. 13446/1980.
However, a fingerprint detection apparatus which relies upon an optical system which employs a rectangular prism is limited in miniaturization of the apparatus because the prism itself has a large size and it is difficult to make the focal length of an optical lens short. Further, since optical parts are used, reduction in cost of the fingerprint detection apparatus is also limited.
Further, the fingerprint detection apparatus which relies upon an optical system has a problem in that, when a finger is too wet or too dry, the fingerprint pattern detected is obliterated or becomes blurred. Therefore, the fingerprint detection apparatus is not sufficiently high in practical use in terms of reliably identifying an individual with certainty under any circumstances.
In order to raise reliability, a fingerprint detection apparatus is proposed in Japanese Patent Laid-Open No. 98754/1995 which does not have a structure wherein a finger is pressed directly against a surface of a prism but has a structure wherein a resilient transparent optical member and a liquid coupling member are interposed between an optical reference surface on which a finger is pressed and a surface of a prism. This structure provides closer contact between the finger and the optical reference surface and allows a stabilized fingerprint pattern to be obtained.
However, with the fingerprint detection apparatus disclosed in Japanese Patent Laid-Open No. 98754/1995 also, the optical principle on the optical reference surface is the same as that when the finger is pressed directly against the prism surface. Therefore, while the fingerprint detection apparatus achieves a little improvement in regard to the problems of reliability as described above, it is still disadvantageous in that, if the finger is sufficiently wet, the fingerprint pattern detected is obliterated, or if the surface on which a finger is pressed is soiled or foreign articles are stuck to the surface, the fingerprint pattern detected is disordered.
As described above it is particularly difficult for fingerprint detection apparatus which rely upon an optical system, to satisfy the demand for miniaturization. Therefore, fingerprint detection apparatus which do not rely upon an optical system have been proposed.
For example, a fingerprint sensor is disclosed in Japanese Patent Laid-Open NO. 27277/1983 wherein resistance elements or piezoelectric elements which have a pressure dependency are used to convert a pressure pattern obtained from concave and convex patterns of a fingerprint when a finger is pressed into a voltage pattern so that the pressure pattern is outputted as an electric signal. The document mentioned further discloses another fingerprint sensor wherein resistance elements or pyro-electric elements which have a temperature dependency are used to convert a temperature pattern obtained from concave and convex patterns of a fingerprint into a voltage pattern so that the temperature pattern is outputted as an electric signal.
The sensors disclosed in Japanese Patent Laid-Open No. 27277/1983 are formed by using an integrated circuit technique which uses silicon crystal. Conversion elements which generate voltage signals from pressures or temperatures are arranged in arrays aligned horizontally and vertically and are covered with a protective film such as an oxide film or a nitride film so that reliability will not be damaged even if a finger touches them directly.
However, such protective films are liable to be broken since they are hard and thin. Therefore, if even a small crack or pinhole is produced in the protective film, then an impurity such as sodium which sticks to the protective film by contact of a finger or the like penetrates through the crack or pinhole and becomes a cause of deterioration of the characteristics of a circuit elements such as a conversion element or a transistor.
As another conventional example of a non-optical fingerprint detection apparatus, a fingerprint sensor which detects the concave and convex configuration of a fingerprint as variations in electrostatic capacity and output the variations as electric signals is disclosed in Japanese Patent Laid-Open No. 231803/1992 and Japanese Patent Laid-Open No. 305832/1996.
In both of the fingerprint detection sensors disclosed, detection elements having detection electrodes covered with an insulating material are arranged in arrays in the row direction and column direction.
Further, the fingerprint detection sensors make use of the principle that, when a finger is pressed against a surface of the insulating material which covers over the detection electrodes, a ridge portion of the fingerprint contacts directly with the insulating material while at a valley portion of the fingerprint an air layer remains between the insulating material and the skin of the finger. Due to this principle, the electrostatic capacity between the surface of the finger and a detection electrode exhibits a higher value at the ridge portion than at the valley portion. An electric signal of a current or voltage whose variated by such a difference in electrostatic capacity as just described is outputted to detect a fingerprint pattern. Also the sensor described above are formed on a chip using an integrated circuit technique which uses silicon crystal similar to the conventional examples described above.
FIG. 1
is a diagrammatic view showing a construction of a fingerprint inputting apparatus disclosed in Japanese Patent Laid-Open No. 305832/2996.
As shown in
FIG. 1
, the present conventional example makes use of the fact that the electrostatic capacity is different in concave and convex portions of a configuration formed by valley lines
518
and ridgelines
519
of a fingerprint pattern against main surface
511
to which a fingerprint is brought near or contacted, and electrically detects the electrostatic capacities in accordance with the concave and convex configuration by detection circuits
513
by using electrodes
512
arranged on main surface
511
at a pitch finer than the line width of the fingerprint.
It is important that the coating of an electric material function also as a protective film for an integrated circuit, but since a protective film of a conventional integrated circuit technique is not formed to cope with the contact of a finger and besides is hard, thin and liable to be damaged, there is a problem in that the characteristics of the integrated circuit is deteriorated by mechanical damage, pollution of the integrated circuit by an impurity, and so forth.
Further, if the surface of the insulating material is soiled with sweat of a finger or the like and the insulation characteristic of the surface is deteriorated, then leak current flows along the surface and decreases the difference in capacitance between a ridge portion and a valley portion of the fingerprint. This gives rise to a problem
NEC Corporaion
Noori Max
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Fingerprint detection apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fingerprint detection apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fingerprint detection apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2466582