JPH02171881A - Fingerprint image input device - Google Patents

Abstract

PURPOSE:To input a rotary stamp picture, for which a finger is rotated on the loading surface of a prism, by dividing a picture, which is inputted from a fingerprint image input part into band-shaped partial area images in a length- wise direction, sampling the images of all the area and after that, synthesizing the images. CONSTITUTION:The image is inputted from a fingerprint image input part 10 and for the image, digital conversion is executed by an A/D converter 11. Then, the image is divided into the band-shaped partial area images in the length-wise direction and the concentration value of a prescribed position image element in the band-shaped partial area images of the image, which is taken in by every time, is detected by a central processing part 15. Then, it is detected that the finger is loaded on the band-shaped partial area images. The band- shaped partial area images are successivelt written to a work memory part 17 and after all the band-shaped partial area images are sampled, the images are synthesized by a synthesization area part 18. Then, a synthesized image is stored to a image storing part 13. Thus, by rotating the finger on the prism reflection surface, the rotary stamp image is inputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image input device, and more particularly to a fingerprint image input device that optically detects a fingerprint image, converts the detected image into an electrical signal, and outputs the signal.

[Conventional technology]

Systems that identify individuals using fingerprints have extremely high reliability due to the characteristics of fingerprints that are "unchangeable throughout life" and "unique for everyone." For this reason, various devices have been proposed that use pattern recognition technology to verify the identity between an input fingerprint and a registered fingerprint registered in advance.

In such a fingerprint identification device, a light source and an ITV (industrial television) are connected to a finger placed on a prism surface by using an optical boundary change from the back side of this placement surface.
It has a fingerprint image input device that generates a photoelectrically converted image of a fingerprint pattern using an image pickup device such as a digital camera (Strial Te1evision) or the like. Examples of such techniques are disclosed in Japanese Patent Application Laid-Open No. 54-69300 and Japanese Patent Application Laid-Open No. 54-85600.

Referring to FIG. 2A, the arrangement relationship between the prism 2 in this image input device and the finger 1, which is the object to be inspected, is shown.

Referring to FIG. 2B, the side view shown in FIG. 2A is shown;
The optical path is also shown. The prism 2 has three independent surfaces: a light entrance surface 21, a reflection surface 22 which is a placement surface on which the finger 1 is placed, and an output surface 23 which guides the reflected light from this reflection surface.

Referring to FIG. 2C, an example of a fingerprint pattern obtained from the deriving surface 23 is shown.

[Problem to be solved by the invention]

However, in this case, since the fingerprint image output from the deriving surface 23 is collected as two-dimensional data, the reflective surface 23
There is a drawback that only a two-dimensional image of the fingerprint of finger 1 in contact with finger 2, that is, only a flat imprint image can be collected.

In addition, by placing a finger on a tubular glass tube, installing a light source and a sensor on the outer periphery of the glass tube in a positional relationship that satisfies the total internal reflection condition, and driving it rotationally, it comes into contact with the inner surface of the glass tube. A fingerprint mapping device for collecting fingerprints is proposed in Japanese Patent Application Laid-Open No. 60-500196. However, as mentioned above, the fingerprint image obtained with this device is limited to only the fingerprint area in contact with the inner surface of the glass tube, and therefore plays an important role during verification due to the discrepancy between the inner diameter of the glass tube and the thickness of the finger. In some cases, it became impossible to input the part called "delta".

It is an object of the present invention, in order to eliminate the above-mentioned drawbacks, to divide a fingerprint image input from a fingerprint image input unit into band-shaped partial area images in the long finger direction, and to detect contact between the fingerprint and the band-shaped partial area images. Detection is made by examining a change in density of a pixel at a predetermined position in the image of the band-shaped partial area in the repeatedly sampled image, and the band-shaped partial area images are sequentially sampled, and the time point when the collection of the endmost band-shaped partial image area is completed. An object of the present invention is to provide a fingerprint image input device that combines all sampled band-like partial region images and obtains a rotary stamp image.

[Means to solve the problem]

The fingerprint image input device according to the present invention includes a prism having three independent surfaces: a light incident surface, a reflecting surface that causes reflection of the light that has passed through the incident surface, and a deriving surface for deriving the reflected light from the reflective surface. In an image input device in which an object to be inspected having a pattern to be verified is placed on the reflective surface and the pattern to be verified is input using light from the derivation surface, a fingerprint placed on the reflective surface; After collecting a fingerprint image, a fingerprint image conversion unit performs photoelectric conversion, an A/D conversion unit converts the photoelectric conversion signal into two-dimensional quantized image data, and , an image input control unit that detects that a fingerprint is placed on a reflective surface and, after the detection, collects at least a part of the input fingerprint; an image synthesis unit that includes a central processing unit, a program memory, a working memory, and an external interface; It is composed of departments.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

Referring to FIG. 1B, one embodiment of the present invention collects an image on the prism 2 surface shown in FIG. A fingerprint image input section 10 for conversion, an analog/digital (hereinafter referred to as A/D) conversion section 11 for converting the electric signal from the fingerprint image input section 10 into two-dimensional quantized image data and outputting it, and this A/D conversion section. An image storage unit 13 stores the signal converted in step 11, and after detecting the gray scale value of a pixel at a predetermined position for the m-th strip area image n i shown in FIG. 1C stored in this image storage unit 13, preset A central processing unit 15 that determines whether or not a finger is placed on the band-shaped area image by comparing it with a threshold value that has been set, and determines whether or not to cut out the band-shaped area image; and a program memory unit 16 that stores a program for synthesizing these; the program stored in the program memory unit 16 is loaded and executed, and band-shaped area images sent from the outside are sequentially written, and all band-shaped area images are collected. A work memory section 17 is a memory area for performing post-synthesis, an input section 12 inputs a processing start signal using a key, a processing start signal from this input section 12 is sent to a central processing section 15, and a result from this central processing section 15 is sent. is sent as various messages, and furthermore, it receives the band-shaped area image data in the image storage section 13 that is cut out according to the instructions from the central processing section 15, and writes it to the work memory section 17 via the central processing section 15. an external interface 14 used to perform the process; an output unit 20 connected via the external interface 14 and outputting the results given from the central processing unit 15 via the external ink interface 14 as various messages; The fingerprint image input unit 1 includes an image input control unit 12 which performs control over whether or not the image is processed in a first central processing unit 15 and, based on the result, the acquisition of the image is performed in the fingerprint image input unit 1.

Next, the operation of one embodiment of the present invention will be described in detail.

Referring to FIG. 1B, in this embodiment, the fingerprint image is input from the fingerprint image input section 10, and the A/D conversion section 11 inputs the
/D converted image consisting of NXN (for example, N=512) pixels is shown in FIG.
=16). Thereafter, in each captured image, the grayscale values of a plurality of pixels at predetermined positions of the above-mentioned band-shaped partial region image n1 (i=o, . . . , k) are detected. When this gradation value exceeds a predetermined threshold value, it is detected that a finger is placed on the above-mentioned band-shaped partial region image. (Step 1 in Figure 1D). Next, the captured NXN image (step 2 in Figure 1D). This process is repeated up to the rightmost band-shaped partial area nk, and after the rightmost band-shaped partial area nk is captured, areas no to nk are synthesized in the synthesis processing section 18 (step 3 in FIG. 1D). Next, the composite image is stored in the image storage section 13. (Step 4 in FIG. 1D) Here, the position of the fingerprint placement detection pixel in the band-shaped partial image area is a predetermined position on the oldest column, center column, or leftmost column in the band-shaped partial image area. , or multiple pixels at random positions within the area. However, here, at the upper end and lower end in FIG. 1C,
Since the finger does not necessarily come into contact during stamping, it is preferable that no finger placement detection pixels be set in this area.

In addition, as a method for setting the aforementioned finger placement detection gradation value, a conventional method is used, and the details thereof will be omitted here.

In the unlikely event that the above-mentioned gray level value of the finger placement comparison pixel does not exceed a predetermined threshold value during finger placement detection, the process is interrupted and the output section 2 A re-stamping request message is displayed to request the user to restart the stamping process.

When compositing the band-shaped partial image areas described above, if the connection of ridges at the boundary between two adjacent areas is unnatural, a weighted average value of the gray values of pixels at both ends of the boundary line may be substituted. It is also possible to perform correction by

In this example, a prism was used as the fingerprint input medium, but trapezoidal distortion on the image due to the triangular shape of the prism can be corrected by known techniques such as affine transformation. The detailed description will be omitted.

In addition, in this example, as shown in the conceptual diagram of FIG. 1A,
The finger is rotated from the left side to the right side on the prism reflective surface. However, by starting the finger device detection process from the rightmost band-shaped partial region in FIG. 1B, it is also possible to collect images of rotational stamping from right to left. Further, finger placement detection is performed alternately in the rightmost band-shaped partial area image and the leftmost band-shaped partial area image, and the band-shaped partial area image is captured from the side on which no finger placement is detected. If so, it is possible to handle rotations from both left and right directions.

〔Effect of the invention〕

According to the present invention, it is possible to input a rotary stamp image by rotating a finger on the mounting surface of the prism.

14...external interface, 15...
...Central processing unit, 16...Program memory unit, 17...Work memory unit, 18...Image synthesis processing unit, 19...Input unit, 20...
...Output section, 21...Incidence surface, 22...
・Reflection surface, 23... Derivation surface.

Agent Patent Attorney Susumu Uchihara

[Brief explanation of the drawing]

1A to 1D are diagrams showing an embodiment of the present invention, and FIGS. 2A to 2C are diagrams showing a conventional fingerprint image input device. In the figure, 1...finger, 2...prism, 10...fingerprint image input section, 11...
・A/D conversion section, 12... Image input control section, 1
3...Image storage unit, Torture 1D

Claims (1)

[Scope of Claims] On the reflective surface of a prism that has three independent surfaces: a light incident surface, a reflective surface that causes reflection of the light that has passed through this incident surface, and a derivation surface that derives the reflected light, In a fingerprint image input device in which an object to be inspected having a pattern is placed and a pattern to be verified is input using light from the deriving surface, an image of the fingerprint placed on the reflective surface is collected; , a fingerprint image input unit that performs photoelectric conversion; an A/D conversion unit that converts the photoelectric conversion signal from the fingerprint image input unit into two-dimensional quantized image data; and a change in density of a pixel at a predetermined position in the collected image. an image input control unit that detects that a fingerprint is placed on the placement surface and, after the detection, collects at least a partial area of the input fingerprint image; a central processing unit, a program memory, a working memory, and an external and an image synthesis processing section consisting of an interface, which divides the image input from the fingerprint image input section into strip-shaped partial region images in the direction of the long finger, and adjusts the position of the finger rotated and pressed on the reflective surface for each region. A fingerprint image input device characterized by detecting the density change by extracting the density change on the band-like partial region image, writing it into a working memory, collecting all the band-like partial region images, and then synthesizing the band-like partial region images. .