JPS58201178A - Fingerprint image input device - Google Patents

Abstract

PURPOSE:To obtain data on invariable the same condition by picking up an image of a finger print when a body is pressed with a finger to pressure at plural points within the same range. CONSTITUTION:The finger 1 is pressed against a prism 2, and its pressure is transmitted to a pressure sensitive part 4 through springs 3. Only when the pressure at each position is greater than a specific value or within some range, the pressure sensitive part 4 turns on, i.e. sends a signal ''1'' to an AND gate 5. When all pressure sensitive parts 4 send out signals ''1'', a controller 6 drives a light source 8 and an image sensor part 7 to pick up an image of the fingerprint.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus that realizes imaging in a uniformly pressed state when a fingerprint image is obtained by pressing a finger against a glass surface or the like without using ink.

Methods for collecting fingerprint images without using ink include pressing the finger against a glass plate and taking images using the reflection of light, and pressing the finger against a prism to capture the contact and non-contact areas of the fingerprint. There are five types of imaging that take advantage of the differences in the paths of light coming from different sources. When collecting fingerprint images by pressing a finger against a glass surface, etc., due to the nature of the finger itself, the degree of unevenness of the pressing force, the strength of the pressing, and the There is a big difference in the fingerprint image obtained depending on the direction of the finger. Therefore, to perform the fingerprint fixation process,
First, it is important to collect fingerprint images under the same conditions as possible. Among these, the problem of the direction of the fingers can be solved by installing a guide or the like and giving instructions, but the problem of unevenness and strength of the force during crimping remains unsolved.

The object of the present invention is to make it possible to capture a fingerprint image while making the bias and strength of this force uniform. The present invention will be explained in detail below.

FIG. 1 shows one embodiment of the present invention, FIG. 1(,) is a side view and a block diagram of the circuit, and FIG.
) and a 7277 diagram of the circuit.

In these figures, 1 is a finger, 2 is a transparent body such as a prism, 3 is a spring, 4 is a pressure sensitive part, 5 is an AND gate, 6 is a controller, T is an image sensor part, 8 is a light source, 9 is an interface, Reference numeral 10 denotes a metal fitting or the like for applying uniform pressure to the pressure sensitive section 4.

The operating principle of FIG. 1 will be explained below. FIG. 1(,) is an example of sensing pressure at four locations as shown in FIG. 1(b). As shown in FIG. 1(,), when the finger 1 is pressed against the prism 2, the pressure is transmitted to the pressure sensitive part 4 via the spring 3. The spring 3 serves to encourage the crimper to correct the crimping by giving a degree of freedom to the movement of the prism 2 in response to the crimping of the finger 1, and also to clarify the difference in the force applied to the four pressure sensitive parts 4. do. In the pressure sensor s4, only when the magnitude of this pressure is above a certain value or within a certain range, an on state, that is, a 1" signal is sent to the pressure sensor 5. This operation causes the pressure sensor at four locations Since this is carried out in all parts 4, the AND gate 5 works to generate a state signal "1" that is ON only when all the pressures in the four parts and the pressures in part 4 are above a certain value or within a certain range. " is sent to the controller 6. Here, the dotted line in FIG. 1(a) indicates the signal line from the pressure sensing section 4 on the side that is not shown in the figure.

Next, the on signal from the AND gate 5 is controlled by the control q-
When the laser 6 receives the light, the light source 8 and the image sensor section T are driven, and a fingerprint image is captured.

The image sensor section T is composed of a high-speed image sensor such as a CCD and a lens system. The fingerprint image captured by the above operations is sent from the interface 9 to another processing section under the control of the controller 6.

In this way, the image sensor section 7. By adopting a method of driving the light source 8, first, it becomes possible to take an image in which the acupressure range is always kept in the same y state. Moreover, since no imaging is performed when the finger pressure is partially offset, distortion of the fingerprint image can be absorbed.

Next, the pressure sensitive section 4 will be explained. The pressure sensitive section 4 functions to generate an ON signal in response to finger pressure and send it to the AND gate 5, and there are two possible types of this. One type generates an on signal when the pressure exceeds a certain value, and the other generates an on signal only when the pressure is within a certain range.

The former has the advantage that it can be easily realized because it can be turned on and off simply by a mechanical contact or a contact using a single sheet of pressurized conductive rubber.

An example is shown in FIG. FIG. 2(a) shows an example of a mechanical contact, and FIG. 2(b) shows an example of a contact using one sheet of pressurized conductive rubber. In Fig. 2, 11A and 11B are metal bodies, 12 is a retention sheet, 13A and 13B are electrodes, 14 is a pressurized conductive rubber,
15 is a substrate.

In the case of the mechanical contact shown in FIG. 2(,), the contraction of the spring 3 causes the metal bodies 11A and 11B to come into contact and become conductive, generating an ON signal.

The pressurized conductive rubber 14 shown in FIG. When pressure is applied by ', the insulation state 14A changes between the tffi 13A and tffi 138 to the conductive state 14B, generating an on signal.

The protective sheet 12° substrate 15 in FIG. 2(b) is involved in contact life and pressure adjustment.

The example of the two contacts shown in Figures 2(a) and (b) is
Although they have the advantage of being easy to implement, they all have the same effect once the pressure exceeds a certain value, so if the force applied to the four pressure sensitive parts 4 in Figure 1 is too strong, the image There is a risk that the image may be captured with distortion. Therefore,
The latter type can be considered to solve this problem. By using this pressure sensitive section 4, it becomes possible to take an image by limiting the range of finger pressure due to the function of the AND gate 5 described above.

This can be achieved as follows.

As shown in FIG. 5, 82 types of pressurized conductive rubber A with different sensitivities are prepared. In FIG. 5, P□+PB is the critical pressure at which the pressurized conductive rubbers A and B become conductive, and the scale on the vertical axis is an example. Pressurized conductive rubbers A and B having such characteristics are commercialized, and specific examples include PCR101 and PCR105 (trade names) manufactured by Nihon Gosei Rubber Co., Ltd.

These two types of pressurized conductive rubbers A and B are combined in two stages as shown in FIG. 13C, 13D in Figure 6
, 13E are electrodes. and a signal S that turns on when each of the pressurized conductive rubbers A and B becomes conductive;
, SB and P shown in FIG.

Another possible method for limiting the pressure range of the pressure sensitive section 4 shown in FIG. 1 is to use a sliding contact as shown in FIG. 9. In FIG. 9, reference numerals 16A and 16B are metal bodies, which contact each other only within a certain range corresponding to the contraction of the spring 3 and become electrically conductive. This is the simplest method for limiting the pressure range of the pressure sensitive section 4.

This concludes the explanation of the pressure sensitive section 4, but as in this embodiment,
If the prism 2 moves due to the spring 3 (in such a case, if the image sensor section I and the light source 8 are fixed, there will be a difference in the image obtained each time the image is taken. Therefore, the image sensor section 7 and the light source 8 are It is necessary to integrate it with the prism 2 so that its relative position does not change at all times.

As explained in detail above, when a fingerprint image is obtained by pressing a finger against a prism or the like, the present invention enables pressure values at multiple locations on the object being pressed to be all within the same range. By taking a fingerprint image at the same time, data in the same state can always be obtained.

This makes it possible to reduce the amount of preprocessing required for fingerprint verification and improve the recognition rate.

Further, since the fingerprint image input device of the present invention can be realized in a small size and at a low price, it has the advantage that it can be easily installed in a home device or the like.

In addition, the switching method of the present invention can be used in applications where turning on and off is performed depending on the magnitude and balance of pressure.

It also has many advantages, such as being able to input other uneven surface information such as rubber stamps in addition to fingerprints.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are a side view, a circuit diagram, a plan view, and a circuit block diagram of an embodiment of the present invention, and FIG. 2(a) is a diagram showing an example of a mechanical contact. , Figure 2(b)
is a diagram showing an example of a contact using one sheet of pressurized conductive rubber, Fig. 3 is an explanatory diagram of the conduction state of pressurized conductive rubber, Fig. 4 is a diagram showing an example of the sensitivity characteristics of pressurized conductive rubber, and Fig. 5 is a diagram showing an example of the sensitivity characteristics of pressurized conductive rubber. The figure shows the sensitivity characteristics of pressurized conductive rubber with different characteristics, Fig. 6 shows an example of a contact made by stacking two sheets of pressurized conductive rubber, and Fig. 7 shows the signal from the contact in Fig. 6. Logic circuit diagram until sending to gate, No. 8
The figure is a pressure diagram of the operation of the contact in Figure 6, and Figure 9 is a diagram showing an example of a sliding contact. In the figure, 1 is a finger, 2 is a prism, 3 is a spring, 4 is a pressure sensitive part,
5 is the 7-dog t, 6 is the fund p-ra, 7 is the image sensor section, 8 is the light source, 9 is the interface, 10 is the metal fittings,
11A and 11B are metal bodies. 12 is a protective sheet, 13A to 13F are electrodes, 14 is a pressurized conductive rubber, 15 is a substrate, 16A and 16B are shown in Fig. 1, Fig. 2 (a); (b) Fig. 3, Fig. 4, Fig. 5, Fig. 7 Figure 8 489-

Claims (6)

[Claims] (1) In an apparatus for obtaining a fingerprint image by pressing a finger against a transparent body, there is provided means for sensing pressure at one or more points on the transparent body to which the finger is pressed, and further, the value of each pressure at the single or plural points. 1. A fingerprint image input device comprising a mechanism for capturing an image of a fingerprint when the total value exceeds a certain value or falls within a certain range. (2) The fingerprint image input device according to claim (1), wherein a spring and a contact are used as means for sensing pressure at a plurality of locations. (3) Pressure as a contact! Fingerprint image input device i according to claim (2), characterized in that it uses an element.
. (4) The fingerprint image input device according to item (2), characterized in that a slide contact is used as the contact. (5) Two types of piezoelectric elements with different characteristics as contacts,
Of these, the one that turns on at a smaller pressure! Claim No. 1, characterized in that it uses a circuit configured with a circuit that takes an AND between the signal from one of the piezoelectric elements and the inverted Ig of the signal from the piezoelectric element that turns on with a large pressure. 2
) Fingerprint image input device described in item 2. (6) The fingerprint image input device according to claim 1, wherein the transparent body and the mechanism for capturing an image of the fingerprint are integrated.