KR20000063878A - Line scan type fingerprint input device - Google Patents

Abstract

PURPOSE: A line scanning apparatus for inputting a finger print is provided to simplify an optical system without many optical sources and diffusing panels, and to reduce the cost of a product, by making a clear image of only one line of a finger print image rather than total finger print images, and adopting a CCD(Charge Coupled Device) with one line or two lines. CONSTITUTION: An optical source(40) is applied to the finger print. A prism(10) changes the path of the light that is reflected by the finger print to guide the light to a sensor(30) for detecting the finger print image. A lens(20) collects the light which is emitted from the prism(10). The sensor(30) with a line type detects the finger print image which passes through the lens(20), and thereby outputs an electrical image signal. The prism(10) includes a finger print input surface(12) which contacts to the finger print, the first reflection surface(14) for reflecting the light which is scattered from the finger print that contacts to the surface(12) by the optical source(40), the second reflection surface(16) for reflecting the light that is reflected by the surface(14), and an emission surface(18) for outputting the light that is reflected by the surface(16).

Description

Line scan type fingerprint input device

The present invention relates to an optical system of a scattering type 1D line scan type fingerprint input device among optical fingerprint input devices.

Fingerprint recognition system (fingerprint recognition system) is a device that compares and recognizes the input fingerprint and the fingerprint of the pre-registered user is a system that is used in various ways, such as locking the door or safe, access control, time and attendance, computer access control. Fingerprint input device (fingerprint input device) is a device that accepts a fingerprint in a fingerprint recognition system, it is classified into optical and non-optical. A fingerprint recognition system employing an optical fingerprint input device is used to reflect a fingerprint image formed on an image sensor (CCD, etc.) by reflecting light on a fingerprint placed on a prism or the like, depending on the valley or ridge of the fingerprint. It is a device that analyzes and compares fingerprints that are stored in advance.

Typical optical fingerprint input devices include absorption type and scattering type.

FIG. 1A is a principle diagram of an absorption type fingerprint input device, and includes a light source 112, a triangular prism 110, a lens unit 114, an image sensor 116, and an image processing unit 125. In the state where the fingerprint is not applied to the fingerprint input window, light emitted from the light source 112 is totally reflected inside the fingerprint input window 118 of the triangular prism 110 and is incident on the image sensor 116 through the lens 114. . When the fingerprint is placed on the fingerprint input window 118, the light is totally reflected from the inner surface of the fingerprint input window 118 to reach the image sensor 116 because the valley of the fingerprint is separated from the fingerprint input window 118, and the ridge of the fingerprint Since the ridge contacts the fingerprint input window 118, light is absorbed without total reflection from the inner surface, so that only a part of the light reaches the image sensor 116. Therefore, the amount of light incident on the image sensor 116 is different depending on the valleys and ridges of the fingerprint, and eventually the image sensor 116 outputs different levels of electrical signals according to the pattern of the fingerprint. The image processor 125 recognizes the fingerprint pattern by shaping the output value of the image sensor 116 into a digital signal and processing the image.

Figure 1b shows a principle diagram of a scattering fingerprint input device. Similar to the case of FIG. 1A, the light source 212, the prism 210, the lens unit 214, and the image sensor 216 are formed, but the prism 210 has a trapezoidal shape, not a triangle. Unlike the absorption formula of FIG. 1A, since light is incident from the light source 212 into the fingerprint input window 218 of the prism 210 at a right angle or much smaller than a critical angle, the valley of the fingerprint not reaching the fingerprint input window 218. In FIG. 2, light does not reach the image sensor through the fingerprint input window 218. In the ridge of the fingerprint, incident light is scattered by the ridge. The scattered light is incident on the lens unit 214 and detected by the image sensor 216.

The fingerprint input device of the above-described method is basically an optical system for acquiring a two-dimensional (surface) fingerprint image, and requires plane light to obtain an image of uniform brightness throughout the fingerprint image. We use adopted light source. In addition, since a nonuniformity of illuminance is not completely solved even by employing a plurality of LEDs, it is common to use a diffuser between the light source and the prism. For these reasons, there is a problem in that power consumption increases and prices rise.

In addition, in order to minimize distortion of the acquired image due to the characteristics of the optical system, a method of employing a plurality of lenses or lengthening an optical path has been proposed, but this causes a increase in the size of the fingerprint recognition module itself.

The present invention has developed a line scan type scattering fingerprint input device to solve the above problems. SUMMARY OF THE INVENTION An object of the present invention is to provide a fingerprint input surface on which a fingerprint is placed, a first reflection surface reflecting a fingerprint image scattered from a fingerprint in contact with the fingerprint input surface by a light source, and a second reflection surface reflecting a fingerprint image reflected from the first reflection surface. The optical system which can acquire a 1-dimensional fingerprint image is employ | adopted by employ | adopting the prism comprised from the 2nd reflection surface and the emission surface which the fingerprint image reflected from the 2nd reflection surface exits to the exterior.

Figure 1a is a principle diagram of the absorbent fingerprint input device.

Figure 1b is a principle diagram of a scattering fingerprint input device.

Figure 2a is a basic optical system of the fingerprint input device according to the present invention

FIG. 2B is a modified embodiment of FIG. 2A

FIG. 2C is another alternative embodiment of FIG. 2A

Figure 3a is a modified embodiment of the fingerprint input window

Figure 3b is another modified embodiment of the fingerprint input window

4 is a modified embodiment of the lens

5 is an embodiment to which the second optical path changing means is applied.

Figure 6a is an embodiment applying the pinhole

Figure 6b is an embodiment to which the slit is applied

Figure 7 is an embodiment to chamfer the prism

<Description of Drawing Main Parts>

Prism 110, light source 112, lens unit 114, image sensor 116, fingerprint input window 118, image processing unit 125, prism 210, light source 212, lens unit 214 , Image sensor 216, fingerprint input window 218, prism 10, lens 20, fingerprint image sensor 30, light source 40, fingerprint input window 12, fingerprint input window 12a , Black coated surface 13, optical insulator coating 13 ', first reflective surface 14, closely coated reflective surface 14a, separately installed reflector 14b, second reflective surface 16, exit surface (18), the cut out portion 19 to reduce the size of the prism, the convex lens 22, the reflecting mirror 50, the pinhole 60, the slit 60 '

Summary of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention basically relates to a scattering fingerprint input device among optical fingerprint input devices, and relates to a fingerprint input device of a one-dimensional (line) sensing method rather than a conventional two-dimensional (surface) sensing method. The present invention basically has the optical structure as shown in Fig. 2A.

That is, in order to detect the light reflected from the fingerprint as an image, the light path changing means for changing the light path irradiated to the fingerprint, the light path of the light reflected from the fingerprint to the destination where the image sensing means is located, and the light emitted from the light path changing means. It consists of a light focusing means for focusing, a line fingerprint image sensing means for detecting the fingerprint image passed through the light focusing means and outputs the electrical image signal.

The light converging means is an optical lens for imaging the light emitted from the optical path changing means onto the fingerprint image detecting means, and the linear fingerprint image detecting means is a one-line or two-line CCD.

The optical path changing means reflects the fingerprint input surface to which the fingerprint is brought into contact with the finger, the first reflecting surface reflecting light scattered from the fingerprint contacted to the fingerprint input surface by the light source, and the light reflected from the first reflecting surface. The second reflecting surface and the light reflected from the second reflecting surface is composed of an exit surface to the outside.

Example

An embodiment of the present invention will be described with reference to the drawings. Figure 2a is a schematic diagram of a line scan type fingerprint input device according to the present invention, in order to detect the light reflected from the fingerprint as an image to detect the fingerprint image by changing the light source 40 irradiated to the fingerprint, the light path of the light reflected from the fingerprint The prism 10 leading to the destination where the sensor 30 is located, the lens 20 focusing the light emitted from the prism 10, and the linear image sensing the fingerprint image passing through the lens 20 and outputting the electrical image signal. It consists of a fingerprint image sensor 30 of the line.

The light irradiated to the valley of the fingerprint in contact with the fingerprint input window 12 does not form an image, but the light irradiated to the ridge of the fingerprint scatters in all directions and is scattered to the prism 10 among the scattered light. Light rays satisfying the imaging condition in the optical system are input to the fingerprint image sensor 30 as a fingerprint image through the lens 20.

Here, since the light source 40 only needs to ensure uniform illuminance in a linear form compared to the two-dimensional fingerprint input device, a small single light source having low power is sufficient (for example, LED).

Lens 20 is to form the light emitted from the prism 10 to the fingerprint image sensor 30, in the present invention, because the fingerprint input is made by the line scan method, even compared to the two-dimensional fingerprint input device A much lower distortion image can be obtained. When acquiring a two-dimensional fingerprint image, the top, bottom, left and right distortion of the image should be considered. However, in the case of 1D line scan, only the left and right distortion of the image should be taken into consideration, so even a small and inexpensive lens can obtain sufficient image quality for fingerprint recognition. have.

A charge coupled device (CCD) or a CMOS sensor may be used as the fingerprint image sensor 30 on the line, and a one-line image sensor used in a general scanner or the like may be used. One-line image sensors are smaller and much less expensive than two-dimensional image sensors. Although not dealt with in the present invention, when a plurality of fingerprint images read in one dimension are synthesized, a two-dimensional image used for actual fingerprint recognition may be obtained. Synthesis of a plurality of fingerprint images read in one dimension into a two-dimensional fingerprint image may be implemented by various methods known to those skilled in the art. Instead of the above-mentioned one-line image sensor, a two-line image sensor can be used to more easily synthesize images (see US Patent No. 6,002,815).

The prism 10 has a trapezoidal shape as shown in FIG. 2A. The prism 10 is scattered from the fingerprint input surface 12 to which the fingerprint is contacted by placing a finger and the fingerprint that is in contact with the fingerprint input surface 12 by the light source 40. The first reflecting surface 14 reflecting light, the second reflecting surface 16 reflecting the light reflected from the first reflecting surface 14, and the light reflected from the second reflecting surface 16 are directed to the outside. It consists of an exit exit face 18. The optical path changing means 10 can also be manufactured in a small size by the linear image sensing characteristic which is a feature of the present invention, thereby reducing the overall optical system size.

In the prism 10 of FIG. 2A, the first reflection surface 14 and the second reflection surface 16 are planes in which total reflection occurs inside the prism. Therefore, the shape of the trapezoidal prism 10 is designed according to the condition that the first reflection surface 14 and the second reflection surface 16 are totally reflected. In addition, the emission surface 18 refracts the light reflected from the first reflection surface 14 and the second reflection surface 16 to the lens 20 and the fingerprint image sensor 30 outside the prism 10. It has an inclination angle to coincide with the optical axis of the path made. This inclination angle will be changed by its refractive index depending on the material of the prism.

On the other hand, although the prism shown in Fig. 2A is manufactured so that total reflection occurs at the first reflection surface 14 and the second reflection surface 16, respectively, in order to facilitate the design of the prism as shown in Fig. 2B. It is also possible to design the total reflection only on the second reflection surface 16 by forming the reflection surface 14a by closely coating the reflector on the first reflection surface. Its implementation can be carried out by chemical vapor deposition (CVD), sputtering or vacuum metal coating and the like and are well known to those skilled in the art.

In addition, as shown in FIG. 2C, instead of the closely coated first reflecting mirror 14a of FIG. 2B, a reflector 14b may be separately installed outside the prism to generate reflection.

Referring to the prism 10 'depicted in Fig. 2c, the first surface 12' on which the fingerprint is placed, the second surface 14 ', which is connected to one end of the first surface and forms a corner, is the second surface 14'. A third surface 16 'connected to one end of the first surface 12' and facing the first surface 12 ', and a fourth surface 18 connecting one end of the third surface 16' and one end of the first surface 12 '. '), And a reflector 14b is separately provided outside the second surface 14'.

The first surface 12 'of FIG. 2C corresponds to the fingerprint input surface of FIG. 2A, the third surface 16' corresponds to the second reflective surface 16 of FIG. 2A, and the fourth surface 18 '. Corresponds to the exit surface 18. The second surface 14 'of FIG. 2C corresponds to the first reflective surface 14 of FIG. 2A, but does not act as a reflection, but light reflected and scattered from the fingerprint contacting the first surface 12' passes through. It serves to be incident to the external reflector 14b. That is, the fingerprint image scattered from the fingerprint in contact with the first surface 12 ′ of the prism 10 ′ of FIG. 2c passes through the second surface 14 ′ and is reflected by the reflector 14b, and then again the second image. Incident through the surface 14 'and totally reflected from the third surface 16' and exit to the fourth surface 18 '.

The reflector 14b may be installed to be in close contact with the outer surface of the prism or may be provided at a predetermined interval d. d may be appropriately set such that the fingerprint image passing through the second surface 14 ′ is incident at an angle at which total reflection occurs on the third surface 16 ′ in consideration of the refractive index according to the material of the prism.

On the other hand, in the line scan type fingerprint input method of the present invention, the fingerprint is input in the area of the fingerprint input surface 12 except for the linear fingerprint input window to block the incidence of external light and to prevent unnecessary reflection of the light inside the prism. The area except the linear window 12a can be processed to form a diffuser. That is, the area except for the window area 12a where the fingerprint is input may be eroded to block unexpected external light incident on the fingerprint input surface as much as possible.

Alternatively, as shown in FIG. 3A, an area except for the fingerprint input window 12a may be treated as the black coating surface 13. This is realized by applying or depositing a paint that can block external light after etching (etching) the region except for the fingerprint input window 12a.

FIG. 3B shows a state where an area of the fingerprint input surface 12 of the prism except the fingerprint input window 12a is etched. That is, after the fingerprint input window 12a is formed to have a step height higher than that of the fingerprint input surface as shown in FIG. 3B, the optical insulator is formed on all surfaces except the fingerprint input window 12a and the exit surface 18. Can cover. This can be implemented by covering the mold formed with a synthetic resin on the prism. This further increases the effect of blocking unnecessary external light incident on the prism. In the embodiment shown in Fig. 2C, when the optical insulation coating is performed, the coating is applied to the areas except for the fingerprint input window, the second surface 14 ', and the fourth surface 18' on the first surface.

In addition, since the fingerprint input surface 12 of the prism 10 is always exposed to the outside, scratches may occur, so that diamond coating, which is commonly used for surface protection, may be performed.

Figure 4 shows an embodiment in which the shape of the lens is different. According to the present invention, since the fingerprint image is basically scanned linearly, the distortion of the image acquired by a small lens or a single lens can be reduced, unlike a fingerprint scan method on a plane (usually a combination of a plurality of lenses aberration) Or correcting distortion). In the case of Fig. 4, it is a diagram showing that the easy-to-fabricated convex lens 22 can be used as the light focusing means.

5, a second optical path changing means, that is, a reflection mirror 50 is added between the lens 20 and the fingerprint image sensor 30, so that the linear distance between the lens 20 and the fingerprint image sensor 30 is added. It is a figure which shows reducing. This allows the entire optical system to be compact.

6A and 6B illustrate an embodiment in which a pinhole 60 or a slit 60 'is additionally disposed between the prism 10 and the lens 20 to improve contrast of a fingerprint image emitted from the prism 10. Indicates.

FIG. 7 illustrates an edge portion 19 that does not affect the fingerprint input surface 12, the first reflective surface 14, the second reflective surface 16, and the exit surface 18 in order to reduce the size of the prism 10. It shows the example which scraped off). Since the fingerprint input device according to the present invention is a line scan type, the fingerprint image does not pass over the entire surface of the exit surface 18 of the prism 10. Accordingly, the size of the edge portion 19 protruding from the prism 10 may be reduced by cutting off the edge portion 19 without affecting the fingerprint image.

As described above, specific embodiments for implementing the technical idea of the present invention have been described. However, the spirit of the present invention is not limited to the above embodiment. The technical idea of the present invention extends to the equivalents in the range partitioned by the claims.

The present invention is a new line scan type fingerprint input device, and the optical system is simplified because only an image is clearly formed on one line instead of the entire image of the fingerprint image, and is used to obtain uniform plane light in a conventional scattered fingerprint input device. It is advantageous in that a large number of light sources, diffusers, and the like are not required. In addition, by adopting a one-dimensional (one or two-line) CCD, it is advantageous in terms of cost of the product than in the case of a two-dimensional CCD. It has the advantage of making it.

Claims (26)

An optical fingerprint input device for detecting light reflected from a fingerprint as a fingerprint image by irradiating a light source to the fingerprint, A fingerprint input surface on which a fingerprint is placed, a first reflecting surface formed by closely coating a reflector to reflect a fingerprint image scattered from a fingerprint in contact with the fingerprint input surface by a light source, and a fingerprint image reflected from the first reflection surface An optical path changing means comprising a second reflecting surface which is totally reflected at a light emitting surface, and an emitting surface at which the fingerprint image reflected by the second reflecting surface is directed to the outside; A light source for irradiating light to the fingerprint input surface through the second reflective surface, An optical lens for focusing a fingerprint image emitted from an exit surface of the optical path changing means, And a line fingerprint image sensing means for detecting a fingerprint image focused by the optical lens and outputting the fingerprint image as an electrical image signal. The method of claim 1, wherein the optical path changing means The fingerprint input surface and the second reflection surface face each other, and the first reflection surface is a quadrilateral prism configured to connect one end of the fingerprint input surface and one end of the second reflection surface. Scan type fingerprint input device. The line scan type fingerprint input device of claim 2, wherein in order to reduce the size of the prism, a part of the exit surface is cut out within a range that does not affect a fingerprint image. The line scan type fingerprint input device according to claim 2 or 3, wherein the fingerprint input surface of the prism has a diffusion plate treatment except for a window in which fingerprints are linearly input. The line scan type fingerprint input device of claim 2 or 3, wherein the fingerprint input surface of the prism is black-coated in an area except for a window in which the fingerprint is linearly input. The line scan type fingerprint input device of claim 2 or 3, wherein the prism is coated with an optical insulator on a region excluding the window and the emission surface on which the fingerprint is linearly input. The line scan type fingerprint input device according to claim 2 or 3, wherein the fingerprint input surface of the prism is coated with diamond. The line scan type fingerprint input device of claim 1, wherein the optical lens is a convex lens. The line scan type fingerprint input apparatus according to claim 1, wherein the linear fingerprint image sensing means is a one-line CCD or CMOS sensor. The line scan type fingerprint input device according to claim 1, wherein the linear fingerprint image sensing means is a 2-line CCD or CMOS sensor. The line according to any one of claims 1 to 3 and 8 to 10, wherein a pinhole or a slit is further disposed between the optical path changing means and the optical lens to improve the contrast of the fingerprint image emitted from the optical path changing means. Scan type fingerprint input device. The line according to any one of claims 1 to 3 and 8 to 10, wherein a second optical path changing means is added between the optical lens and the fingerprint image sensing means to reduce the linear distance between the optical lens and the fingerprint image sensing means. Scan type fingerprint input device. 12. The line scan type fingerprint input device of claim 11, wherein a second optical path changing means is added between the optical lens and the fingerprint image sensing means to reduce the linear distance between the optical lens and the fingerprint image sensing means. An optical fingerprint input device that detects light reflected from the fingerprint as a fingerprint image by irradiating a light source to the fingerprint, A first surface on which the fingerprint is placed; a second surface connected to one end of the first surface to form an edge; a third surface connected to one end of the second surface and facing the first surface; one end and a first surface of the third surface An optical path changing means consisting of a fourth surface connecting one end of the And reflecting means provided in proximity to the outside of the second surface of the optical path changing means, The fingerprint image scattered from the fingerprint in contact with the first surface of the optical path changing means passes through the second surface, is reflected by the reflecting means, then enters through the second surface, is totally reflected from the third surface, and exits to the fourth surface. Characterized in that A light source for irradiating light to the fingerprint input surface through the third surface of the optical path changing means, an optical lens for focusing a fingerprint image emitted from the fourth surface of the optical path changing means, and focused by the optical lens A line scan type fingerprint input device further comprising a linear fingerprint image detecting means for detecting a fingerprint image and outputting the fingerprint image as an electrical image signal. The method of claim 14, wherein the optical path changing means A quadrilateral prism formed of the first, second, third, and fourth surfaces, wherein the fourth surface may image the fingerprint image totally reflected on the third surface to the fingerprint image sensing means through an optical lens. Line scan type fingerprint input device, characterized in that formed in the refraction angle exiting at an angle. The line scan type fingerprint input device of claim 15, wherein a portion of the fourth surface is cut out within a range that does not affect a fingerprint image in order to reduce the size of the prism. The line scan type fingerprint input device according to claim 15 or 16, wherein the first surface of the prism has a diffusion plate treatment except for a window in which fingerprints are linearly input. The line scan type fingerprint input apparatus of claim 15 or 16, wherein the first surface of the prism is black-coated in an area excluding a window in which the fingerprint is linearly input. The line scan type fingerprint input apparatus of claim 15 or 16, wherein the prism is coated with an optical insulator on a window in which the fingerprint of the first surface is linearly input, and an area other than the second and fourth surfaces. 17. The line scan type fingerprint input device according to claim 15 or 16, wherein the first surface of the prism is diamond coated. 15. The line scan type fingerprint input device according to claim 14, wherein the optical lens is a convex lens. 15. The line scan type fingerprint input device according to claim 14, wherein the linear fingerprint image detection means is a one-line CCD or CMOS sensor. 15. The line scan type fingerprint input device according to claim 14, wherein the linear fingerprint image sensing means is a 2-line CCD or CMOS sensor. The line according to any one of claims 14 to 16 and 21 to 23, wherein a pinhole or a slit is further disposed between the optical path changing means and the optical lens to improve the contrast of the fingerprint image emitted from the optical path changing means. Scan type fingerprint input device. The line according to any one of claims 14 to 16 and 21 to 23, wherein a second optical path changing means is added between the optical lens and the fingerprint image sensing means to reduce the linear distance between the optical lens and the fingerprint image sensing means. Scan type fingerprint input device. 25. The line scan type fingerprint input device of claim 24, wherein a second optical path changing means is added between the optical lens and the fingerprint image sensing means to reduce the linear distance between the optical lens and the fingerprint image sensing means.