JPS60114979A - Finger print input device - Google Patents

Abstract

PURPOSE:To obtain a finger print input device inputting a finger print image with less curved distortion as a front image by inputting directly the finger print image from a finger of a human being, converting and outputting it as an electric signal. CONSTITUTION:A light generated from a light source 4 is reflected on a half mirror 7 and reaches a transparent plate 2. A coating layer exists at the inside of the transparent plate 2 and most of the light is transmitted without being reflected on this face and reaches the external surface of the transparent plate 1. This light reaches a finger without being reflected on the outer surface of the transparent plate at a ridge line where the transparent plate and the finger are contacted closely and absorbed. On the other hand, the depths between ridge lines are not contacted with the transparent plate. Thus, the light is reflected partly on the outer surface of the transparent plate. As a result, the depths are seen brightly. Thus, a finger print image having a high contrast is obtained. The half of the luminous amount of the image is lost by the half mirror, but the remaining half reaches a picture sensor 5, where it is converted into an electric signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a fingerprint input device that directly inputs a fingerprint image from a human finger, converts it into an electrical signal, and outputs it.

[Background of the invention]

In order to directly input a fingerprint image from a human finger, as shown in FIG. is necessary.

By the way, the conventional technique shown in FIG. 1 has the following problems.

Since the transparent plate 2 is fixed to the support base 3, forces are applied to the fingers unconsciously placed on the transparent plate in the in-plane and dimensional directions as well as in the in-plane rotational direction, and as a result, The obtained fingerprint image has curvature distortion in one-dimensional direction and rotational direction.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a fingerprint input device that inputs a fingerprint image with little curvature distortion as a front image.

[Summary of the invention]

In order to achieve the above object, a fingerprint input device based on the principle shown in FIG. 2 was invented. 1 is a finger. E is a transparent plate, 3 is,
The support base 7 that supports the transparent plate is a lubricating device that allows smooth horizontal translation and rotational movement of the support base with respect to the transparent plate. Reference numeral 8 denotes a spring for keeping the transparent plate in a fixed position relative to the main body when no finger is placed on the transparent plate. In the present invention, by employing a good lubricating device 7 and a spring 8 having a minimum necessary spring constant, the transparent plate is freely supported in the horizontal direction. As a result, conventionally,
When a finger is pressed against the transparent plate, any horizontal and horizontal rotational forces that the finger has been subjected to are released, the curvature distortion of the finger skin is significantly reduced, and a fingerprint image with less curvature distortion is obtained.

Furthermore, reflection of light on the inner surface of the transparent plate 2 significantly reduces the contrast of the fingerprint image. In order to prevent this and obtain good contrast, it is essential in the present invention to provide a coating layer (not shown) on the light source side surface of the transparent plate.

Note that in order to obtain a front image, the light from the light source is irradiated perpendicularly to the transparent plate. This can be easily realized by using a half mirror as shown in the following example.

[Embodiments of the invention]

FIG. 3 shows an embodiment of the present invention. 4 is a light source;
5 is an image sensor that converts a fingerprint image into an electrical signal. 7
is a half mirror.

The light emitted from the light source 4 is reflected by the half mirror 7 and reaches the transparent plate 2. There is a coating layer (not shown) on the inside of the transparent plate 2, and most of the light passes through this surface without being reflected and reaches the outer surface of the transparent plate 1. This light reaches the finger and is absorbed without being reflected by the external surface of the transparent plate at the ridge portion where the finger is in close contact with the transparent plate. As a result, when you look at your finger from inside the transparent plate, the ridges appear dark. on the other hand,
The valley portion between the ridges does not contact the transparent plate.

Therefore, some of the light is reflected from the outer surface of the transparent plate. As a result, this valley part appears bright.

In this way, a fingerprint image with high contrast is obtained. This image loses half of its light intensity due to the half mirror, but the remaining half reaches the image sensor 5 and is converted into an electrical signal.

When the transparent plate on which the fingers are placed is in a stationary state, no force is applied to the fingers in the horizontal or horizontal direction, in order to achieve a state close to the ideal rolling between the transparent plate and the support base.
In this embodiment, a ball bearing is used as the lubricating device. This is shown in Figures 3-(b) and (c). 3rd-
FIG. 3(b) is a sectional view taken along the cross-section A-A in FIG. 3-(a). Figure 3-(c) is the cross section B- of Figure 3-(b).
It is an i-plane view in B. This bearing has a circular shape as shown in Fig. 3-(b) in consideration of ease of machining. The transparent plate is also circular. Spring 8 is a leaf spring.

As a result of the above, a fingerprint image with less curvature distortion can be obtained. Also,
It is clear that the obtained fingerprint image is a frontal image.

〔Effect of the invention〕

The main points of the present invention are summarized below.

(1) By allowing two smooth horizontal rotations of the transparent plate, when the transparent plate is stationary, the force that the finger receives from the transparent plate is only in the vertical direction, making it possible to obtain a fingerprint image with less curvature distortion. .

(2) By combining a single-sided coated flat transparent plate and a half mirror, a high contrast fingerprint image can be obtained as a front image.

Note that if a frontal image is not necessarily required, the fourth
The embodiment shown in the figures makes it possible to obtain images with an even simpler structure and higher contrast. Here, a right angle prism 2'' is fixed to the transparent plate 2' at its center.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional example, and FIG. 2 is a diagram of the principle of the present invention.
3 and 4 show an embodiment of the present invention. 2...Transparent plate (flat plate coated on one side). 3... Support stand, 4... Light source, 5... Image sensor,
. 6... Guide plate, 7... Half mirror 28... Leaf spring. 9... Lubricating device. Figure 1 Figure 2 Figure ■ 3 Continuation of Figure 1 page @ Inventor Shigeo Shiono [Phase] Inventor Takaya Hayashi @ Inventor Hiroshi Hyo - ■ Inventor Mitsuru Kosaka 1-1-1 Kokubun-cho, Hitachi City Hitachi, Ltd., Kokubu Factory, 109 Hata, Ozenji, Tama-ku, Kawasaki City, Hitachi, Ltd., System Development Laboratory

Claims (1)

[Claims] (2) A fingerprint input device comprising a transparent plate, means for holding the transparent plate movably in parallel to the surface thereof, and a device for capturing an image of a fingerprint of a finger placed on the transparent plate.