JPH0127471B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fingerprint image identification system that directly collects, identifies, and collates the uneven pattern of a fingerprint in real time.

[Conventional technology]

FIG. 4 is a system diagram showing a conventional fingerprint image input device disclosed in, for example, Japanese Unexamined Patent Publication No. 55-13446. 4 is an optical device configured to make the light beam from the light source 1 enter at an angle within a certain range; 4 is a conversion device for converting optical information from this optical device into an electrical signal to obtain a fingerprint image; 5 is a converting device for obtaining a fingerprint image; This fingerprint image is captured and identified. This is a processing device that performs verification, etc.

Next, the operation will be explained. By making the incident light beam 6 from the light source 1 incident on the surface 3a of the optical device 3, such as a right-angle prism, having transmission and reflection characteristics, and making the incident light beam 6 on the slope 3b at an angle exceeding the critical angle 7, Total reflection occurs at the interface between the slope 3b of the rectangular prism 3 made of a transparent material such as glass and air, and no total reflection occurs at the interface where the finger 2 is in close contact due to the relationship of the refractive indexes of the media. In other words, the trough line 2a portion of the fingerprint that is not in close contact with the slope 3b is totally reflected, and the ridge 2b portion of the fingerprint that is in close contact with the slope 3b is not totally reflected, so that a contrasting fingerprint pattern can be obtained. The reflected light beam 8 on the slope 3b is transmitted through the surface 3c, and this optical information is converted into an electrical signal by a conversion device 4 such as a television camera, and is taken into the processing device 5 as an image.

[Problem that the invention seeks to solve]

In conventional fingerprint image input devices such as those described above, even if a finger is placed on the slope of a rectangular prism, moisture such as sweat and oil comes out on the surface of the finger and the contact with the slope does not improve, resulting in a difference in contrast. I couldn't get a clear image and had to wait a while for the moisture to come out. Therefore, especially with dry fingers, a blurred image may be transferred to the processing device without waiting for the surface to become moist, which may lead to incorrect identification or later errors. There was a problem that was difficult to resolve.

The present invention has been made to solve these problems, and an object of the present invention is to provide a fingerprint image identification system that allows accurate identification and verification by constantly importing clear fingerprint images with contrast into a processing device.

[Means for solving problems]

The fingerprint image identification system of the present invention includes an optical device that allows a light beam from a light source to enter at a predetermined angle onto a surface on which a finger of a subject is placed, and converts optical information from this optical device into an electrical signal. a conversion device that obtains a concavo-convex pattern of a fingerprint image, an arithmetic device that divides the concavo-convex pattern into partial regions and calculates the dispersion ratio of density in each partial region, and a calculation device that calculates the contrast of the fingerprint image by comparing the dispersion ratio with a reference value. It is equipped with a discrimination device that discriminates the presence or absence of fingerprints, a display device that informs the subject of the discrimination results, and a processing device that captures, identifies, and collates fingerprint images that are determined to have contrast by the discrimination device.

[Effect]

The discrimination display device of the present invention can be used, for example, when a finger is not placed on the right-angle prism, when the finger is placed and waiting for moisture to come out on the surface of the finger, or when the finger is in close contact with the right-angle prism. A clear fingerprint image with contrast is obtained, and the state of the input fingerprint image is determined based on the dispersion ratio of the density in the partial area. It is possible to reliably capture a clear fingerprint image of the subject without relying on the fingerprint.

[Embodiments of the invention]

FIG. 1 is a system diagram showing an embodiment of the present invention, and numerals 1 to 8 in the figure are the same as the conventional device. Reference numeral 9 indicates whether or not the finger 2 is placed on the slope 3b of the rectangular prism based on the density distribution of the image obtained from the conversion device 4 such as a television camera. This is an automatic determination device that automatically determines whether it is acceptable to import
0 indicates the three cases in which the test subject is informed of the discrimination result.
A display device consisting of LEDs 10a to 10c,
The discrimination display device is an automatic discrimination device 9 having a calculation function.
and a display device 10.

In the initial state where the finger 2 is not placed on the slope 3b of the rectangular prism, the LED-1 of the display device 10 is
10a lights up and prompts the subject to place finger 2 on it. Next, when the subject places finger 2, the LED-110a
disappears, the LED-210b blinks, and the subject waits for moisture to appear on the surface of the finger, and the subject has to wait in that state for a while. Furthermore, when the adhesion between the finger 2 and the slope 3b increases, a contrasting and clear uneven pattern of the fingerprint image can be obtained. At this point, this fingerprint image is taken into the processing device 5 and the LED-210b
disappears, and the LED-310c lights up, indicating that a clear fingerprint image has been obtained and taken into the processing device 5. The processing device 5 identifies fingerprints. Processing such as verification begins, and the subject may remove the finger 2 from the slope 3b. When these processes are completed, the LED-310c goes out, and the LED-110a lights up again, returning to the initial state. The above three states are determined based on the density distribution of the image obtained from the conversion device 4 such as a Tervi camera.
The automatic discrimination device 9 automatically performs this.

The algorithm is shown in the flowchart of FIG.

(i) As shown in the explanatory diagram of FIG. 3, consider, for example, four regions (11).

(ii) Image 1 is the third state where finger 2 is not placed.
The image in Figure a is captured and the density variance σ _i ⁽¹⁾ (i=1, . . . , 4) in the four regions (11) in (i) is calculated.

(iii) Take the state in which finger 2 is placed (Fig. 3b) as image 2, and calculate the density variance σ _i ⁽²⁾ (i = 1, ..., 4) in the four regions (11) of (i). calculate.

(iv) Calculate R=min iσ _i ⁽²⁾ /σ _i ⁽¹⁾ .

(v) When R≦T ₁ (T ₁ ; standard value of dispersion ratio 1), consider that this is a state in which finger 2 is not placed,
The LED-110a lights up, prompts the subject to place finger 2, and returns to (iii).

(vi) When T ₁ <R≦T ₂ (T ₂ ; reference value of dispersion ratio 2), this is considered to mean that the surface of the finger is still dry, and LED-110a goes out and LED-21
0b flashes, prompting the subject to wait for a while, and returning to (iii).

(vii) When R>T ₂ , it is assumed that a high contrast image has been obtained, and the LED-210b turns off.
LED-310c lights up.

In the above embodiment, three LEDs 10a to 10c were used as the display device 10, but depending on the above three states, "Please put your finger on it.""Please wait for a while.""Please take your finger off." You may also use a text display board that displays a message such as ".

〔Effect of the invention〕

As described above, according to the present invention, there is provided an optical device in which a light source beam from a light source is made incident at a predetermined angle on a surface on which a finger of a subject is placed, and an electrical signal that transmits optical information from this optical device. A conversion device that converts the uneven pattern into a fingerprint image to obtain an uneven pattern, and an arithmetic device that divides the uneven pattern into partial areas and calculates the variance ratio of density in each partial area.The contrast of the fingerprint image is determined by comparing the variance ratio with a reference value. By incorporating a discrimination device that determines the presence or absence of fingerprints, and a processing device that captures, identifies and collates fingerprint images that are determined to have contrast by this discrimination device, it is possible to always capture clear images with contrast. This has the effect of providing a fingerprint image identification system that can perform accurate identification and verification.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a fingerprint image identification system according to an embodiment of the present invention, FIG. 2 is a flowchart of an embodiment of an automatic discrimination device according to the present invention, and FIG.
The figure is an explanatory diagram of the flowchart shown in Figure 2,
The figure is a system diagram showing a conventional fingerprint image input device. In the figure, 1 is a light source, 2 is a finger, 3 is an optical device, 4 is a conversion device, 5 is a processing device, 9 is an automatic discrimination device, and 10 is a display device, and 9 and 10 constitute a discrimination display device. . In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An optical device that allows a beam of light from a light source to be incident at a predetermined angle on the surface on which the finger of the subject is placed; converts the optical information from this optical device into electrical signals to generate the uneven pattern of the fingerprint image. conversion device to obtain,
an arithmetic device that divides the uneven pattern into partial regions and calculates the dispersion ratio of density in the partial regions; a discriminator that compares the dispersion ratio with a reference value to determine the presence or absence of contrast in the fingerprint image; A fingerprint image identification system comprising: a display device that informs the subject of the discrimination result; and a processing device that captures, identifies, and collates a fingerprint image that is determined to have contrast by the discrimination device.