Image analysis – Applications – Personnel identification
Reexamination Certificate
1997-12-04
2001-02-06
Mehta, Bhavesh (Department: 2721)
Image analysis
Applications
Personnel identification
C356S071000
Reexamination Certificate
active
06185319
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a fingerprint input apparatus for inputting fingerprints to register them or collate them with fingerprints already registered.
None of the fingerprints of different people coincide with each other, and the fingerprints do not change throughout their lives. Owing to these characteristics of fingerprints, fingerprint collation systems are especially used in the fields that require high degrees of security. An apparatus for inputting fingerprint images is a constituent element of such a fingerprint collation system. This fingerprint input apparatus includes an optical system as a constituent. The collation precision of the fingerprint collation system greatly depends on whether fingerprint images can be correctly input.
Any conventional fingerprint input apparatus, however, cannot obtain high-quality fingerprint images.
SUMMARY OF THE INVENTION
The present invention has been made to solve this problem, and has as its object to provide a fingerprint input apparatus which can obtain high-quality fingerprint images.
In order to achieve the above object, according to the first aspect of the present invention (according to claim
1
), there is provided a fingerprint input apparatus comprising a prism placed such that a surface in one direction serves as a fingerprint collection surface, a light source for irradiating light on the fingerprint collection surface through the prism, a pinhole set in a path of light which is reflected by a pattern surface of a finger placed on the fingerprint collection surface and emerges from the prism, and an imaging plane on which the light emerging from the prism and passing through the pinhole is formed into an image, wherein when the prism is substituted by air, an optical fingerprint collection surface equivalent to the fingerprint collection surface is set to be substantially parallel to the imaging plane.
According to this aspect, light reflected by the pattern surface of the finger directly or indirectly placed on the fingerprint collection surface and emerging from the prism passes through the pinhole and is formed into an image on the imaging plane set to be almost parallel to the optical fingerprint collection surface of the prism.
According to the second aspect of the present invention (according to claim
2
), in the first aspect, when the optical fingerprint collection surface has distortion with respect to the fingerprint collection surface, the imaging plane is rotated through a predetermined angle. According to this aspect, distortion caused on the optical fingerprint collection surface can be reduced by rotating the imaging plane almost parallel to the optical fingerprint collection surface of the prism through a predetermined angle.
According to the third aspect of the present invention (according to claim
3
), there is provided a fingerprint input apparatus comprising a first prism placed such that a surface in one direction serves as a fingerprint collection surface, a light source for irradiating light on the fingerprint collection surface through the first prism, a pinhole set in a path of light which is reflected by a pattern surface of a finger placed on the fingerprint collection surface and emerges from the first prism, an imaging plane on which the light emerging from the first prism and passing through the pinhole is formed into an image, and a second prism placed in front of the imaging plane, wherein the fingerprint collection surface of the first prism is set to be substantially parallel to the imaging plane, the fingerprint collection surface of the first prism is set to be substantially parallel to a surface of the second prism on the imaging plane side, and an exit surface of the first prism with respect to the pinhole is set to be substantially parallel to an incident surface of the second prism with respect to the pinhole.
According to this aspect, the optical system on the first prism side is made similar to the optical system on the second prism side with the pinhole being the center, and light reflected by the pattern surface of the finger directly or indirectly placed on the fingerprint collection surface and emerging from the first prism passes through the pinhole and the second prism and is formed into an image on the imaging plane.
According to the fourth aspect of the present invention (according to claim
4
), in the first, second, and third aspects, the apparatus further comprises pinhole position adjusting means for adjusting a position of the pinhole. According to this aspect, the position and size of a fingerprint image on the imaging plane can be changed by adjusting the position of the pinhole in the back-and-forth direction, the lateral direction, the vertical direction, and the like.
According to the fifth aspect of the present invention (according to claim
5
), in the fourth aspect, the pinhole position adjusting means is constituted by a manual adjusting mechanism, and the apparatus further comprises a display section for displaying a fingerprint image formed on the imaging plane. According to this aspect, the user can change the position and size of a fingerprint image on the imaging plane by adjusting the position of the pinhole in the back-and-forth direction, the lateral direction, the vertical direction, and the like while seeing the displayed fingerprint image.
According to the sixth aspect of the present invention (according to claim
6
), the pinhole position adjusting means automatically adjusts the position of the pinhole. According to this aspect, the position of the pinhole is automatically adjusted, and the position and size of a fingerprint image on the imaging plane are adjusted to set values.
According to the seventh aspect of the present invention (according to claim
7
), in the first, second, and third aspects, the light source is an LED or a laser beam radiator. According to this aspect, light from an LED or a laser beam radiator, i.e., light having a single wavelength, is irradiated on the fingerprint collection surface through the prism.
According to the eighth aspect of the present invention (according to claim
8
), there is provided a fingerprint input apparatus comprising a prism placed such that a surface in one direction serves as a fingerprint collection surface, a light source for irradiating light on the fingerprint collection surface through the prism, a pinhole set in a path of light which is reflected by a pattern surface of a finger placed on the fingerprint collection surface and emerges from the prism, a lens placed close to a rear side of the pinhole, and an imaging plane on which the light emerging from the prism and passing through the pinhole and the lens is formed into an image, wherein when a straight line connecting a center of the fingerprint collection surface and a center of the imaging plane is an optical axis, the imaging plane is inclined with respect to the optical axis to prevent a blur, and a central axis of the lens is inclined with respect to the optical axis to prevent trapezoidal distortion.
According to this aspect, the light intensity of a fingerprint image formed on the imaging plane is increased by the lens placed close to the rear side of the pinhole. In this case, a blur is suppressed by inclining the imaging plane with respect to the optical axis, and trapezoidal distortion is suppressed by inclining the central axis of the lens with respect to the optical axis under the condition in which this blur is suppressed.
According to the ninth aspect of the present invention (according to claim
9
), in a fingerprint input apparatus based on the optical path separation method, a cut surface is formed at a distance from a vertex of the prism which opposes the fingerprint collection surface, and the light source is placed to oppose the cut surface, of the prism. According to this aspect, light from the light source is incident on the prism through the cut surface to be irradiated on the fingerprint collection surface with an almost uniform diffusion angle.
According to the 10th as
Blakely & Sokoloff, Taylor & Zafman
Mehta Bhavesh
Yamatake - Honeywell Co., Ltd.
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