JPH04120671A - fingerprint input device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fingerprint input device used for fingerprint verification, verification identification, and the like.

[Prior Art] In order to put fingerprints to practical use as a means of personal identification, it is desirable to have a simple inkless fingerprint input device that places less psychological and physical burden on the user. In addition, it is possible to obtain an image with good contrast between the ridges and valleys of the fingerprint.
It is necessary to have a reading accuracy of about 0 μm in order to facilitate subsequent processing.

Conventionally, there are two types of input devices for fingerprint recognition: those that use light emitted from the laser tip of substances contained in skin secretions, and those that use changes in the reflected light when the finger touches a glass surface (fingerprint recognition). Automatic identification technology, Masahiro Kawagoe, Measurement and Control, Vol. 25 No. 8pp, 701-7
069). In many cases, the prism method J is used. In this prism method, the slope of the prism is illuminated by total internal reflection from the inside of the glass, and the specularly reflected light from the inner surface of the glass is imaged using an imaging optical system outside the prism. The image is formed on the element, and when inputting a fingerprint image, the finger is pressed against this slope.When the finger is pressed, the convex part of the fingerprint makes contact with the skin and the glass, so the reflected light is reflected. It is scattered and does not reach the image sensor.Using this principle, it is possible to obtain a fingerprint image with strong contrast.

(Co-author, Automatic Classification of Fingerprint Patterns, Kawagoe 1 Building, Information Processing Society of Japan Research Report, Computer Vision, 18-2.19
(Refer to 82) Furthermore, a method has been devised in which the contrast is improved by placing an image sensor in an area where the scattered light from the recessed part of the fingerprint does not reach. (Refer to ``Fingerprint information detection method using a prism'' by Shimizu et al., National Conference of the 74th Communication Society, 1311, 1984) [Problem to be solved by the invention] In this method, Keystone distortion occurs due to different optical paths.

■Superimposition of "noise light" due to the previous user's residual fingerprint■
Miniaturization is difficult in principle because it requires an optical system for imaging outside the prism.

There are some problems such as.

Furthermore, in order to avoid the influence of residual fingerprints, a device has been devised that uses a hologram to input a two-dimensional image of the ridge pattern of a fingerprint. (Refer to Personal Verification Device Using Holographic Fingerprint Sensor, by Igaki et al., Institute of Electronics, Information and Communication Engineers Research Report, Pattern Recognition and Understanding, 88-38, 1988) However, it is equipped with a means for touching the fingerprint or a glass surface, etc. Input devices have the problem of superimposition of noise light due to residual fingerprints of previous users, making it difficult to extract features of fingerprints. When a prism is used on the fingerprint contact surface, trapezoidal distortion occurs due to the optical path to the image sensor being different for each point of the fingerprint, and there is a risk that the fingerprint image will be further distorted due to misalignment of the finger contact position. Furthermore, since there are individual differences in the wetness of fingertips, the fingerprint image may be blurred or unclear for some people. A two-dimensional image sensor that directly captures an image of the fingerprint surface has been considered, but if the entire fingerprint surface is not illuminated uniformly, an uneven fingerprint image will be input, which will cause problems in fingerprint verification. I will do it.

The present invention directly images the ridges and valleys of the fingerprint surface with a one-dimensional line image sensor without bringing the fingerprint into contact with a glass surface or the like (non-contact state), thereby eliminating the influence of residual fingerprints and uneven illumination. The purpose is to make it possible to input a fingerprint image that is not available.

[Means for Solving the Problems] In order to solve the above problems, the present invention has a structure that includes a guide portion that guides the fingerprint surface of a finger to be input to a predetermined position, and an opening window that opens corresponding to the assumed position of the fingerprint surface. a one-dimensional line image sensor arranged to focus on the assumed fingerprint surface position, a lighting device that illuminates the assumed fingerprint surface position, the one-dimensional line image sensor and the lighting device. a driving means for integrally moving the one-dimensional line image sensor, a moving amount detecting means for detecting the moving amount of the one-dimensional line image sensor, and a one-dimensional image is captured and synthesized based on the output signal of the detecting means to produce a two-dimensional image. and a fingerprint input control means.

The driving means may preferably be one that moves in a curve along the fingerprint surface, but it may also be one that moves linearly in the front-rear direction or left-right direction.

Furthermore, in order to automatically operate the device, an imaging switch that is activated at the top of the finger inserted into the finger guide is provided at the back of the finger guide. The image pickup switch may be of an optical type or a mechanical type.

[Operation] When the fingertip is guided to a predetermined position along the finger guide and the imaging switch is turned on, a part of the non-contact fingerprint is imaged on the one-dimensional line image sensor through the aperture window, and a one-dimensional image is formed. By integrally moving the line image sensor and the illumination device, one-dimensional images with uniform illumination are continuously captured, and by synthesis, a two-dimensional fingerprint image with uniform illumination is input.

Furthermore, by moving the one-dimensional line image/sensor and the illumination device in a curve along the fingerprint surface, it is possible to input even the fingerprint on the side of the finger.

Furthermore, by providing an imaging switch at the back of the finger guide that operates at the top of the finger inserted into the finger guide, a fingerprint image can be input by simply guiding the fingertip to a predetermined position along the finger guide.

[Example] An embodiment of the present invention will be described below.

FIG. 1 is a configuration diagram showing an embodiment of the fingerprint input device of the present invention, and includes a cylindrical finger guide 1 for inserting a fingertip, and a finger guide 1 provided corresponding to the assumed position of the fingerprint surface. an imaging switch 2 disposed on the inner surface of the finger guide 1 and operated by an inserted fingertip; and an imaging switch 2 disposed in the direction of insertion of the finger and receiving an imaging start signal based on the detection of the fingertip of the switch 2. A one-dimensional line image sensor 3 (hereinafter referred to as an image sensor) that images a part of a fingerprint using a cylindrical lens 4, and a cylindrical lens 4, which are arranged in a pair in parallel with the image sensor 3 and are connected through the aperture window 1a. an illumination device 5 that illuminates the assumed fingerprint surface position, an image sensor 3, a lens 4. A support stand 6 that integrally supports the illumination device 5, a drive device 7 and a crankshaft 8 that rotate the support stand 6 about the central axis of the cylindrical surgical guide 1 and along the opening window 1a, An angle sensor 9 detects the rotation angle of the drive device 7, and outputs an imaging start signal to the image sensor 3, illumination device 5, and drive device 7 based on the input signal from the imaging switch 2, and outputs an output signal from the angle sensor 9. Continuously transfer the one-dimensional images captured based on the image to the synthesis buffer 10,
It also includes a CPU II that controls controls such as outputting a two-dimensional fingerprint image from the synthesis no.7 surface 10.

It should be noted that the CPU II has a signal line with an external interface in addition to the synthesis bus 10.

The illumination device 5 uses two linear light sources, such as fluorescent tubes, to illuminate the image sensor 3 from both sides so that the color tone of the fingerprint is uniform. Further, the resolution determined by the lens 4 and the image sensor 3 is arranged so that the object can be captured at 20 pixels/my to 30 pixels/wry. The maximum depth of focus of lens 4 is 2vt
, 11, so as to absorb the difference in height of the fingerprint surface and clearly capture the fingerprint image, it is preferable to use one with a depth of focus of 2u or more.

Next, the fingerprint input operation of the above device will be explained.

A subject who inputs a fingerprint image moves his or her fingertip along the finger guide 1 of the cylindrical lock from the first joint to the second joint. When the imaging switch 2 is pressed and turned ON while the fingerprint surface is within the imaging range of the image sensor 3 through the opening window 1a, a signal indicating fingertip detection (imaging possible) is sent to the CPU II.

The CPU l 1 receives the signal, outputs a lighting signal to the lighting device 5, and initializes the synthesis buffer 10. Illumination light from the illumination device 5 is reflected on the fingerprint surface through the opening window 1a provided in the finger guide 1, and enters the lens 4 as reflected light, which produces shadows between the ridges and valleys of the fingerprint. is formed on the image sensor 3 as a one-dimensional grayscale image. In that state,
When a drive start signal is output from the CPU II to the drive device 7 and an imaging signal is output to the image sensor 3, the signal becomes 1.
The dimensional image g(θ) is transferred to the synthesis buffer 10. θ
represents the detected rotation angle of the angle sensor 9, and Cp is calculated every time the detected rotation angle θ becomes a positive multiple of the rotation angle σ corresponding to the pixel pinch.
It is set so that an imaging signal is output from the ull to the image sensor 3. Therefore, each time the drive device 7 rotates by the rotation angle σ, a one-dimensional image g(θ1) is transferred to the synthesis buffer 10, and a two-dimensional image is obtained by synthesis.

Figure 2 (a) shows an image sensor using the rotation of the drive device.
Fig. 2(b) shows the relationship between the rotation of No. 3 and the fingertip, and FIG.

FIG. 2 is a schematic diagram in which a two-dimensional fingerprint image is synthesized after being transferred to a file 10; Note that the rotation angle σ is preferably set so that the pixel pitch is 50 μm or less.

When the drive device rotates by a predetermined rotation angle θe, a reverse rotation signal is output from the CPU to the drive device and the image/sensor 3
is returned to the initial rotation angle θS, the imaging operation is completed, and the input of the fingerprint image is completed.

FIG. 3 shows a flowchart of the above imaging operation.

In the above embodiment, by integrally moving the one-dimensional image sensor and the illumination device, one-dimensional images with uniform illuminance are continuously captured, and by combining two-dimensional images with uniform illuminance.
A dimensional fingerprint image is input.

Furthermore, it is possible to input a fingerprint image with an even pitch over a wide range over the entire surface (both sides) of the fingertip where the fingerprint is located.

Therefore, even if the fingerprint at the center of the fingerprint surface is worn or scratched, it does not interfere with fingerprint verification or fingerprint identification.

FIG. 4 is a configuration diagram of an embodiment in which the image 7 sensor, lens, and illumination device are integrally moved horizontally, in which 101 is a finger guide, 101a is an aperture window, 102 is an image pickup switch, 10
3 is one-dimensional line image sensor-104 or lens, 1
05 is a lighting device, 106 is a support stand, 107 is a drive device,
108 or guide rail, 109 or angle sensor 110
or synthesis buffer, 111 or CPU, 112 or pulley 1
13 or Held.

Next, since the principle is the same as that of the embodiment shown in FIG. 1, the fingerprint input operation will be briefly explained.

The fingertip is advanced along the finger guide 101 to take an image.

When the key 102 is pressed and turned on, the lighting device 105 lights up and the synthesis/nofa 110 is initialized.

When a drive start signal is output from the CPt; l 11 to the drive device 107 and an imaging signal is output to the image sensor 103, a one-dimensional image is transferred to the synthesis buffer 100. When the drive device 107 rotates, the pulley 112 or heald 113 is moved, and the support base 106 is moved horizontally along the guide rail 108, and the image sensor 103, lens 104, etc. The illumination device 105 moves horizontally as a whole.

Then, every time the rotation angle detected by the angle sensor 109 becomes a positive multiple of the rotation angle corresponding to the pixel pitch, an imaging signal is output from the CPUIQQ to the image 7 sensor 103, and a one-dimensional image of horizontal movement or a composite haphazard sofa 100 is output. The images are transferred and combined to obtain a two-dimensional image.

When the drive device 107 rotates to a predetermined rotation angle, the CPU
A reverse rotation signal is output from 111 to the drive device 107, and the image sensor 103 is returned to its initial rotation angle, and the imaging operation is completed, and the input of the fingerprint image is completed. In the embodiment described above, one-dimensional images with uniform illuminance are continuously captured by moving the image sensor and the illumination device together, and a two-dimensional fingerprint image with uniform illuminance is input by synthesis. In this embodiment, the moving direction of the support base 106 may be the front-back direction.

The present invention is not limited to the above-mentioned embodiments, but the finger guide is configured such that the fingerprint surface is inserted at an appropriate angle from upward to 90 degrees left and right, and the lens surface and image sensor are inserted at an appropriate angle from downward to 90 degrees left and right. By arranging it at a suitable angle, the optical system faces downward, making it less susceptible to falling dust.

Furthermore, by providing two cylindrical parts in the finger guide and inserting two fingers at the same time, it is possible to prevent the fingertips from shifting in the rotational direction. That is, from an ergonomic point of view, if two or more fingers are inserted into the cylindrical part, the fingers will not rotate. Then, by providing an opening window in each cylindrical part and simultaneously capturing a plurality of fingerprint images using two image sensors and performing verification processing in parallel, the ambiguity of fingerprint recognition can be reduced and reliability can be improved.

Further, by notifying the user of the fingerprint input status and completion, it is possible to give the user a sense of security.

[Effects of the Invention] The fingerprint input device according to the present invention collects fingerprint images without contacting with a glass surface, etc., so it is not affected by residual fingerprints at all. By moving the one-dimensional line image sensor and the lighting device together, one-dimensional images with uniform illumination can be captured continuously.
Since a two-dimensional fingerprint image with uniform illumination is input through synthesis, it can greatly contribute to the realization of a device with high recognition performance.

In addition, if a driving means is adopted that moves the one-dimensional line image sensor and the light source in a curve along the assumed fingerprint surface corresponding to the opening window of the finger guide, it can be used to move the one-dimensional line image sensor and the light source in a curved line along the assumed fingerprint surface corresponding to the opening window of the finger guide. You can input evenly pitched fingerprint images into the .

Therefore, there is an advantage that even if the fingerprint at the center of the fingerprint surface is worn out or scratched, it will not interfere with fingerprint verification or fingerprint identification.

Furthermore, since fingerprint collection is automatically performed by simply inserting the fingertip into the finger guide, the operation is extremely simple.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a first embodiment of the fingerprint input device of the present invention, and FIG. 2(a) is an image sensor in the first embodiment.
A relationship diagram showing the relationship between the rotation of and the fingertip, Figure 2 (b) is 1
FIG. 3 is a flowchart according to the present invention, and FIG. 4 is a configuration showing a second embodiment of the fingerprint input device of the present invention. It is a diagram. Code 1.101...Finger guide, Ia, 101a/Opening window 2.1.02...Image sensor 3.103...One-dimensional line image~/Sensor 5.10
6...Lighting device, 6.106...Support stand, 7.107...Drive device, 9.109...Angle sensor 10.11.0...Composition buffer, 11.111...CPU0 substitute Person Patent Attorney Ume 1) Katsu (2 others) (a) Figure 2 10 (41A) Guno 1r) (b)

Claims (1)

[Claims] 1. A finger guide having a guide portion that guides the fingerprint surface of a finger to be input to a predetermined position and an opening window that opens corresponding to the assumed position of the fingerprint surface; and a finger guide that focuses on the assumed position of the fingerprint surface. a one-dimensional line image sensor disposed at a location, a lighting device for illuminating the assumed fingerprint surface position, a driving means for integrally moving the one-dimensional line image sensor and the lighting device, and the one-dimensional line image sensor. a movement amount detection means for detecting the movement amount of the fingerprint surface; and a fingerprint input control means for capturing a one-dimensional image based on the output signal of the detection means and synthesizing it into a two-dimensional image; A fingerprint input device characterized by directly capturing images of ridges and valleys. 2. The fingerprint input device according to claim 1, further comprising driving means for moving the one-dimensional line image sensor and the light source in a curve along an assumed fingerprint surface corresponding to the opening window of the finger guide. 3. The fingerprint input device according to claim 1, further comprising an imaging switch operated at the top of the finger inserted into the finger guide.