JPH03194675A - Finger image input device - Google Patents

Abstract

PURPOSE:To obtain a finger image of high quality by attaching a warming means to the attaching face of a finger placing base with a wedge-shaped member between them. CONSTITUTION:A heater 15 is adhered to a face R of a prism 11 with a wedge- shaped member 16 between them and is attached at an angle to the attaching face R of the prism 11 by this wedge-shaped member 16. When the temperature of a finger placing face T of the prism 11 is raised to the value required for sweating after the start of warming of the prism 11, a finger F is placed on the finger placing face T. Since the heat from the heater 15 approximately simultaneously reach the face T by the wedge-shaped member 16 in this case, the temperature distribution on the finger placing face T is approximately uniformized. Consequently, the finger F equally sweats, and uneven contact of the finger F to the prism 11 is prevented. Thus, a vivid and uniform finger image including the fingerprint or the like is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a finger image input device used in, for example, a personal authentication device that authenticates an individual using a fingerprint.

(Prior Art) In recent years, personal authentication devices that use finger images such as fingerprints as personal identification information have been developed.

One type of finger image input device often used in this type of personal recognition device is an optical path separation method using a prism. Regarding this optical path separation method, Akira Shimizu and Masahiko Hase: “Fingerprint information detection method using a prism,” Journal of the Institute of Electronics and Communication Engineers Vol.

J67-D Magneto 5, pp, 627-628 (1984
-4).

FIG. 3 shows a finger image input device that employs the optical path separation method.

That is, a light source (illumination means) is placed opposite to the surface S of the optical prism (finger rest) 1 having a right-angled isosceles triangular cross-sectional shape, which is one of the two sides intersecting at right angles in the cross section of the prism 1. 2 and a camera (imaging means) 3 are respectively disposed, and another surface R is coated with a light shielding member 4 to prevent light from entering there. Then, with the finger F in contact with the finger rest surface T sandwiched between the surface R and the surface S, an image of the finger F is captured by the camera 3 by allowing light from the light source 2 to enter through the surface S. It has become so. In this case, the surface (belly) of the finger F has countless irregularities such as fingerprints and wrinkles at the joints, and the light from the light source 2 is emitted only at the part where the finger F and the finger rest surface T are in contact. The light is diffused, and only a portion of this diffused light is captured by the camera 3 as a finger image.

Incidentally, the quality of the obtained finger image largely depends on the degree of close contact between the finger F and the prism 1. Therefore, a heater (heating means) 5 is attached to the surface R of the prism 1, and the heater 5 warms the prism 1 to promote sweating of the finger F, thereby increasing the adhesion between the finger F and the prism 1. A device that can obtain a detailed finger image is being considered.

However, when installing the heater 5 of the prism 1,
has an inclination with respect to the finger position T. For this reason,
As shown in the figure, when the heater 5 is installed parallel to the point R, the way the heat is transmitted to the a section and the b section of the prism 1 is different. That is, as can be seen from the shape of the prism 1, heat is transferred to the section a faster than the section b. In such a case, the temperature on the finger resting surface T of the prism 1 becomes uneven, and the fingers F do not sweat uniformly. Therefore, the finally obtained finger image is partially unclear, resulting in poor quality.

(Problem to be Solved by the Invention) As described above, in the conventional finger image input device, since the heater is installed parallel to the surface of the prism that is inclined with respect to the finger placement surface, the temperature at the finger placement surface is Also, the perspiration of the fingers becomes non-uniform, making it difficult to obtain sharpness for a portion of the finger image.

Therefore, an object of the present invention is to provide a finger image input device that can maintain a uniform temperature distribution on the finger rest surface of a finger rest and can obtain a finger image that has uniform clarity throughout. There is.

[Structure of the Invention] (Means for Solving Problems) In order to achieve the above object, the finger image input device of the present invention includes a transparent finger rest having a cross-sectional shape of a right isosceles triangle. and a heating means for warming the finger rest; an illumination means for illuminating the finger placed on the finger rest; and an imaging means for taking an image of the finger illuminated by the illumination means; In a device that inputs a finger image by contacting and non-contacting the finger and the finger rest, the heating means:
A wedge-shaped member is provided for attaching the finger rest at an angle to the attachment surface.

(Function) According to the present invention, the heating means is attached to the attachment surface of the finger rest via the wedge-shaped member by the above-described means, so that heat is transferred to the finger rest surface of the finger rest. It is possible to equalize the transmission of sweat over time, and also to equalize the sweating effect of the fingers, so that the fingers can be brought into close contact with the finger rest evenly.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a finger image input device of the present invention.

That is, the optical prism 11 serving as a finger rest has a cross-sectional shape of a right isosceles triangle, and the angle between the surface S and the surface R thereof forms a right angle. Then, the finger F is placed on a surface (finger rest surface) T sandwiched between the surface S and the surface R.

A light source 12 as an illumination means and a camera 13 as an imaging means are arranged on the prism 11 so as to face the surface S, respectively.

The camera 13 is located at a position where the reflected light from other than the finger rest surface T of the prism 11 is not captured, that is, from among the light that is reflected by hitting the unevenness such as a fingerprint on the surface (belly) of the finger F or wrinkles at the joint part, the camera 13 It is arranged in a position where the light that hits and is reflected cannot reach.

Further, the surface R of the prism 11 is coated with a black light shielding member 14 for absorbing light. A heater 15 as a heating means is attached to the black-coated surface R of the prism 11.

FIG. 2 shows how the heater 15 is attached to the surface R of the prism 11.

That is, the heater 15 is bonded to the surface R of the prism 11 via the wedge-shaped member 16, and the wedge-shaped member 16 allows the heater 15 to be mounted at an angle with respect to the mounting surface R of the prism 11. ing. In this case, the wedge-shaped member 16 is made of silicone rubber, for example, and the heater 15 for the part a or part b of the prism 11 is
It functions so that the heat transfer time from the

Next, the operation in such a configuration will be explained.

First, when the power of the apparatus is turned on, the power to the heater 15 is turned on and heating of the prism 11 is started. Then, the temperature of the finger rest surface T of the prism 11 is at an appropriate temperature (
When the temperature reaches the temperature required for sweating, the finger F is placed on the finger placement surface T. Then, the finger F is encouraged to sweat due to the heat received from the prism 11, thereby increasing the adhesion between the finger F and the prism 11.

In this case, since the wedge-shaped member 16 is set so that the heat from the heater 15 reaches parts 0 and a, and parts d and b almost simultaneously, the temperature distribution on the finger rest surface T is It can be made almost uniform. therefore,
The fingers F sweat evenly, and uneven contact between the fingers F and the prism 11 can be eliminated.

When the finger F is placed on the finger placement surface T of the prism 11, the light source 12 enters from the surface S of the prism 11.
The finger F on the finger rest surface T is illuminated by the light from. In this case, the surface (belly) of the finger F has countless irregularities such as fingerprints and wrinkles at the joints. Therefore, the light from the light source 12 is diffusely reflected at the portion where the prism 11 and the finger F are in contact, and is totally reflected or transmitted through the prism 11 at the other non-contact portions.

Of the light that is reflected by hitting the unevenness of the finger F due to the illumination of the light from the light source 12 on the finger resting surface T of the prism 11, the light that is totally reflected by hitting the concave portion that the finger F is not in contact with is reflected by the prism. The light is guided to the surface R of 11 and absorbed by the light shielding member 14.

On the other hand, the light that hits the convex portion that is in contact with the finger F is diffusely reflected at this portion, and a portion of the light is imaged by the camera 13. This allows the convex parts to be bright and the concave parts to be dark.
A high quality (uniform sharpness) finger image including fingerprints etc. can be obtained.

Note that after the light transmitted through the prism 11 is diffusely reflected by the finger F, a portion of the light is returned to the prism 11 again, but is not captured by the camera 13.

As described above, the heater is mounted obliquely at a predetermined angle with respect to the inclined surface of the prism.

That is, the heater is attached to the prism so that the heat from the heater reaches the entire finger resting surface of the prism almost simultaneously. This makes it possible to make the temperature distribution on the finger resting surface uniform, so that the perspiration of the fingers can be made even. Therefore, even in environments where necessary and sufficient sweating cannot be obtained, it is possible to improve the adhesion of the fingers to the prism, and it is also possible to eliminate uneven adhesion.
This makes it possible to obtain an even, high-definition finger image without partially losing clarity.

In the above embodiment, the wedge-shaped member is made of silicone rubber. However, the wedge-shaped member is not limited to this. It is also possible to use plastics or the like.

Furthermore, the present invention is applicable to various finger image input devices that input, for example, a finger image of only a fingerprint portion, or a finger image of a finger metal body including wrinkles appearing at the ii joint or the second joint portion.

It goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] As detailed above, according to the present invention, the heater is attached at a predetermined angle to the surface of the prism that is inclined with respect to the finger rest surface. It is possible to provide a finger image input device that can maintain a uniform temperature distribution on a finger resting surface and can obtain a finger image that has uniform sharpness throughout.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a finger image input device showing an embodiment of the present invention, FIG. 2 is a diagram for explaining the installation of a heater, and FIG. 3 is a diagram for explaining the prior art and its problems. FIG. 11... Optical prism (finger rest), 12... Light source (illumination means) 13... Camera (imaging means), 15.
...Heater (heating means), 16...Wedge-shaped member, F...
·finger.

Claims (1)

[Claims] A transparent finger rest having a cross-sectional shape of a right isosceles triangle, a heating means for warming the finger rest, an illumination means for illuminating the finger placed on the finger rest, and illuminated by the illumination means. In the finger image input device, the finger image input device includes an image capturing means for capturing an image of a finger, and inputs a finger image depending on whether the finger and the finger rest are in contact or non-contact. A finger image input device characterized in that a wedge-shaped member is provided for mounting at an angle with respect to a mounting surface.