KR20040025968A - Finger print input apparatus capable of preventing remaining image input - Google Patents

Abstract

PURPOSE: A device for inputting an optical fingerprint to prevent the afterimage input is provided to prevent the afterimage input due to an external light source by using a light source difficult to be detected from the outside as an internal light source and making an image sensor react to the internal light source. CONSTITUTION: A light path changer(111) is equipped with a fingerprint input window(110) and changes a light path by reflecting/refracting light. A lighting system(100) includes the internal light source emitting the light of a specified wavelength range from the wavelength range except the wavelength range of the light inputted from the outside and controls the internal light source in order to emit the light to the fingerprint input window. A filter(120) passes only the light corresponding to the wavelength range from the light changing the light path by the light path changer. The image sensor(140) outputs an electric image signal by receiving the light passed the filter. An image processor(150) formalizes the electric image signal output from the image sensor into a digital signal and recognizes a fingerprint pattern by processing the digital signal.

Description

Optical fingerprint input device which can prevent afterimage input {FINGER PRINT INPUT APPARATUS CAPABLE OF PREVENTING REMAINING IMAGE INPUT}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fingerprint recognition device, and more particularly, to an optical fingerprint input device which prevents an afterimage caused by a fingerprint (hereinafter referred to as a residual fingerprint) remaining in a fingerprint input window in which an individual's finger fingerprint is in contact.

Recently, the importance of biometrics as a method of identifying an individual is gradually increasing.

Biometrics refers to performing personal identification using an individual's unique physical or behavioral characteristics.

The unique characteristics of the individual include a finger fingerprint, a hand shape, an eye iris, a face, a vein pattern on the back of the hand, a voice pattern, and the like, and each feature has a difference in user convenience, intimacy, and recognition performance.

Among the unique features of the individual, the fingerprint recognition device for identifying an individual through a finger fingerprint is a device that compares and recognizes an input fingerprint with a fingerprint of a pre-registered individual, and locks a door or a safe, access management, time and attendance management, and computer. It is widely used for access control.

In order to perform the fingerprint recognition, a fingerprint input device which receives a fingerprint is largely divided into optical and non-optical methods, and in the case of an optical fingerprint input device, a fingerprint placed on a prism or the like illuminates a light generated by an internal light source to generate a valley or a fingerprint. According to the shape of the ridge (ridge) is reflected and the fingerprint image formed on the image sensor is analyzed and contrasted with the previously stored fingerprint.

Typical optical fingerprint input devices include absorption and scattering.

1 is a block diagram of a general absorption fingerprint input device.

As shown in FIG. 1, a general absorption type fingerprint input device includes a light source 3, a triangular prism 1, a lens unit 5, an image sensor 7, and an image processing unit 11. The light source 3 is used by arranging a plurality of LEDs, and the triangular prism 1 is a right triangle and is a prism in which total reflection occurs inside the fingerprint input window 9 when there is no fingerprint input. The image sensor 7 is an element that outputs a corresponding electric signal according to the amount of light input such as a CCD or CMOS sensor, which is well known to those skilled in the art. The inclined surface of the triangular prism 1 is a fingerprint input window 9 for placing a fingerprint to be input, and the inner surface of the fingerprint input window 9 is a total reflection surface causing total reflection.

The light emitted from the light source 3 while the fingerprint is not applied to the fingerprint input window 9 is totally reflected inside the fingerprint input window 9 of the triangular prism 1 to the image sensor 7 through the lens 5. Incident. When the fingerprint is placed on the fingerprint input window 9, the light is totally reflected from the inner surface of the fingerprint input window 9 to reach the image sensor 7 because the valley of the fingerprint is separated from the fingerprint input window 9, and the ridge of the fingerprint Since the light comes into contact with the fingerprint input window 9, light is absorbed without total reflection from the inner surface, so that only a part of the light reaches the image sensor 7.

Therefore, the amount of light incident on the image sensor 7 is different depending on the valleys and ridges of the fingerprint, and eventually the image sensor 7 outputs electric signals having different levels according to the pattern of the fingerprint. The image processor 11 recognizes a fingerprint pattern by shaping the output value of the image sensor 7 into a digital signal and processing the image.

2 is a block diagram of a general scattering fingerprint input device.

As shown in FIG. 2, the general scattering fingerprint input device may include a light source 22, a prism 20, a lens unit 24, and an image sensor 26 similarly to the absorption fingerprint input device illustrated in FIG. 1. Although constructed, the prism 20 has a trapezoidal shape rather than a triangle. Unlike the absorbing fingerprint input device of FIG. 1, since light is incident from the light source 22 into the fingerprint input window 28 of the prism 20 at a right angle or an angle smaller than the critical angle, the light input does not touch the fingerprint input window 28. In the valley of the fingerprint, the light does not reach the image sensor 26 through the fingerprint input window 28, and in the ridge of the fingerprint, incident light is scattered by the ridge. The scattered light is incident on the lens unit 24 and detected by the image sensor 26.

3 is another configuration diagram of a general scattering fingerprint input device.

As shown in FIG. 3, in the fingerprint input device, light does not reach the image sensor 36 by passing through the fingerprint input window 38 in the valley of the fingerprint that does not touch the fingerprint input window 38, and the ridge of the fingerprint. In Principle, the incident light is scattered by the ridge, but the difference is that the prism 30 in the form of an isosceles triangle is used and the position of the light source 32 is changed.

In the case of an absorption type fingerprint input device, light is absorbed from the ridge, so that the fingerprint image formed on the image sensor has a dark ridge and a bright valley. On the other hand, in the scattered fingerprint input device, light scattering occurs in the ridge, so that the fingerprint image formed on the image sensor has bright ridges and dark valleys, resulting in a fingerprint image opposite to the absorption type. However, in order to ease the processing of the fingerprint image and to prevent the black and white from appearing inverted depending on the input method, the scattered fingerprint input device is inverted and displayed on the computer monitor. That is, the fingerprint image formed on the actual image sensor has bright ridges and dark valleys, but the gray level in the fingerprint image processing process has a low value at the ridges and a high value at the valleys as in the absorption method.

However, in the case of such an optical fingerprint input device, the previous fingerprint is left by sebum or contaminants according to the contact of the fingerprint in the fingerprint input window where the individual's fingerprint is in contact, and at this time, an external light source coming from the outside instead of an internal light source, For example, when light is incident at a certain range of angles from sunlight or electric light, an afterimage of the remaining fingerprint may be detected by the image sensor. When the image sensor detects such an afterimage, the fingerprint recognition device may mistake the afterimage as the actual biometric fingerprint. Therefore, a problem may arise in which an unauthorized person has access authentication by the afterimage buried in the fingerprint input device instead of inputting his fingerprint.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and to prevent the residual image input by the external light source by using a light source that is difficult to be detected externally as an internal light source and allowing the image sensor to respond only to the internal light source. To provide an optical fingerprint input device that can be.

1 is a block diagram of a general absorption fingerprint input device.

2 is a block diagram of a general scattering fingerprint input device.

3 is another configuration diagram of a general scattering fingerprint input device.

4 is a block diagram of an optical fingerprint input device capable of preventing afterimage input according to an exemplary embodiment of the present invention.

FIG. 5 is a structural diagram of the optical fingerprint input device shown in FIG. 4.

FIG. 6 is a diagram illustrating an example of a structure of an optical bandpass filter used in the filter unit illustrated in FIG. 4.

FIG. 7 is a view illustrating that the filter part of FIG. 4 is formed by combining a low pass filter and a high pass filter.

8 is a view illustrating that light by an external light source is blocked by the filter unit of FIG. 4.

FIG. 9 is a view illustrating passage of light emitted from an internal light source by the filter unit of FIG. 4.

Optical fingerprint input device according to a feature of the present invention for achieving the above object,

An optical fingerprint input device for obtaining a fingerprint image of light reflected by irradiating an internal light source to a fingerprint,

An optical path changing unit having a fingerprint input window on which a fingerprint is placed and changing an optical path by reflecting or refracting light; An illumination system including an internal light source for irradiating light of a specific wavelength region among wavelength regions other than a wavelength range of light input from the outside, and controlling the internal light source to irradiate light to the fingerprint input window to make an image of a fingerprint; A filter unit configured to pass light corresponding to a wavelength range of light emitted from the internal light source among light whose optical path is changed by the optical path changing unit; An image sensor unit receiving the light passing through the filter unit and outputting the corresponding electric image signal; And an image processing unit for shaping an electrical image signal output from the image sensor unit into a digital signal and processing the image to recognize a fingerprint pattern.

The optical fingerprint input device further includes a lens unit for focusing the light passing through the filter unit and inputting the light to the image sensor unit.

Here, the internal light source is characterized in that for irradiating light in the infrared region having a longer wavelength than the visible wavelength range.

In addition, the internal light source is characterized in that for irradiating blue light of the short wavelength region of the visible light.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a block diagram of an optical fingerprint input device capable of preventing afterimage input according to an exemplary embodiment of the present invention, and FIG. 5 is a structural diagram of the optical fingerprint input device shown in FIG. 4.

As shown in FIGS. 4 and 5, an optical fingerprint input device according to an embodiment of the present invention includes an illumination system 100, a prism 110, a filter unit 120, a lens unit 130, and an image sensor unit 140. ) And an image processor 150.

The illumination system 100 includes an internal light source, for example, a plurality of LEDs arranged in a particular shape, and controls the light by the internal light source to be used for fingerprint input through the prism 100.

As an internal light source included in the illumination system 100, a light source that emits light having a wavelength that is difficult to detect in general nature, that is, a wavelength other than the wavelength that may correspond to an external light source such as sunlight or a lamp light, may be used. Preferably, an infrared region (wavelength region in the range of 0.8 μm to 1 mm) longer than the visible region (generally in the range of 400 nm to 800 nm) or a blue series which is the shorter wavelength region in the visible region It is effective to use a light source that emits light in the wavelength range of 400 nm to 500 nm.

Since the use of the light source of the long wavelength region and the light source of the short wavelength region should be determined in conjunction with the characteristics of the sensor used in the image sensor unit 140 for detecting the light of the internal light source will be described later.

The prism 110 may have various shapes according to the type of the fingerprint input device, and reflects and refracts the light irradiated by the internal light source of the illumination system 100 to the fingerprint in contact with the fingerprint input window 111 on which the fingerprint is placed. The light path is changed to guide the filter unit 120.

The filter unit 120 includes a band pass filter through which light irradiated by the internal light source passes and filters light by the external light source, which is an image sensor unit 140 that detects light of the internal light source. It is used to increase the responsiveness of the sensor. That is, only light corresponding to the wavelength region (infrared region or blue series) of the internal light source of the illumination system 100 is passed among the light irradiated to the filter unit 120. Such bandpass filters, particularly optical bandpass filters, have already been The optical filter of is known.

As shown in the accompanying FIG. 6, the optical bandpass filter includes a plurality of metal layers 210, 220, 230, and 240 each having a thickness of λ / 4 on a transparent support 200 such as glass. In the lamination, a vacuum deposition method or the like is used, and the metal layers 210, 220, 230, and 240 are coated on the transparent support 200.

In addition, the metal layer is made of Mg metal layers 210 and 230 or Fe metal layers 220 and 240, and the metal layers 210, 220, 230 and 240 are alternately stacked.

As described above, each of the metal layers 210, 220, 230, and 240 stacked on the transparent support 200 reflects / absorbs light in a specific wavelength band, that is, in a wavelength region of light emitted by an external light source, and in other wavelength bands, that is, inside The light in the wavelength region of the light irradiated by the light source passes through, thereby exhibiting the effect of the bandpass filter.

In general, in the case of the low pass filter, the metal layers are stacked in 38 to 45 layers, and in the case of the band pass filter, the metal layers are stacked in about 100 layers or more.

The bandpass filter may be a bandpass filter formed by combining a lowpass filter LPF and a highpass filter HPF, as shown in FIG. 7.

The lens unit 130 guides the light that is guided by the prism 110 and passes through the filter unit 120 to be input to the image sensor unit 140.

The image sensor unit 140 includes, for example, a CCD or a CMOS sensor, and outputs a corresponding electric signal according to the amount of light input through the lens unit 130.

The CMOS sensor of the image sensor 140 is specified according to an internal light source, and when the internal light source is a light source of an infrared wavelength having a long wavelength, an infrared sensor that can detect light in the infrared region should be used. If the light source is a short wavelength blue light source, a blue light sensor capable of detecting such blue light should be used.

The long wavelength infrared image sensor has good response characteristics, and has a wide pass band, making it easy to design a band pass filter of the filter unit 120, and a relatively low price of an infrared light source, which is a corresponding internal light source. On the other hand, since the amount of light present in the infrared band in the real world is relatively large, the amount of light that is irradiated from an external light source and passes through the filter unit 120 and inputs to the image sensor unit 140 is relatively high, resulting in afterimages. The prevention rate can be lowered.

On the other hand, the short wavelength blue image sensor has relatively poor response characteristics compared with the long wavelength infrared image sensor, and the price of the blue light source, which is a corresponding internal light source, is relatively high. Since the light present in the series is relatively small, the amount of light irradiated from the external light source and passed through the filter unit 120 and input to the image sensor unit 140 is also relatively small, so that the afterimage prevention rate is relatively high.

Therefore, depending on the surrounding environment including the location where the fingerprint input device is to be used, the long-wavelength infrared light source and its bandpass filter and image sensor are used or the short-wave blue light source and the bandpass filter and image sensor are used. Should be determined.

The image processor 150 recognizes a fingerprint pattern by shaping an electrical signal output from the image sensor 140 into a digital signal and processing the image.

As described above, a bandpass filter that uses an internal light source in a wavelength region that is hardly present as an external light source in the illumination system 100 and passes only light corresponding to the wavelength region of the internal light source from the light emitted through the prism 110. And an image sensor 140 that detects the amount of light corresponding to the wavelength region of the internal light source from the light collected by the lens unit 130 after passing through the band pass filter 120. In this case, as shown in FIG. 8, light from an external light source is input to the filter unit 120 through the prism 110, but the light does not pass through the bandpass filter of the filter unit 120 and is blocked. Can be.

However, as shown in FIG. 9, light emitted from the internal light source of the illumination system 100 is totally reflected inside the fingerprint input window 111 of the prism 110 and input to the filter unit 120, and the filter The band pass filter of the unit 120 is the light of the internal light source is light in the wavelength region corresponding to the band pass so that it can be irradiated to the image sensor unit 140 through the lens unit 130. Thereafter, the image sensor unit 140 outputs an electric signal corresponding to the amount of incident light, and the image processing unit 150 forms a digital signal and images the electrical signal output from the image sensor unit 140 to process a fingerprint pattern. Will be recognized.

Therefore, even though the light emitted from the internal light source and the light from the external light source are mixed to pass through the prism, only the light emitted from the internal light source is passed through the filter unit 120. Afterimages will not appear. That is, the filter unit 120 and the image sensor unit 140 achieves the effect that the afterimage input by the external light source is prevented.

On the other hand, the above has been described taking the absorption fingerprint input device as an example, it will be readily understood by those skilled in the art that the scattered fingerprint input device can be equally applied to the case.

In addition, although the internal light source has been described as only irradiating long-wavelength infrared light or short-wave blue light compared to the wavelength of visible light, the technical scope of the present invention is not limited thereto, and the wavelength range of the light input to the external light source and Of course, the light source for irradiating light of the other wavelength region may be applied even if not in the infrared region or the blue series. In this case, a band pass filter through which light of a corresponding wavelength may pass is used in the filter unit 120, and the sensor of the image sensor unit 140 should be a sensor capable of detecting light of the corresponding wavelength. Without the above example it will be taken for granted.

In addition, in the infrared region having a long wavelength, the light emitted from the external light source is relatively higher than that of the blue series, but even in this case, the light detected by the filter unit 120 and the image sensor unit 140 is increased. It should be noted that the amount of can be ignored since it is very small compared to the amount of light that is detected by the internal light source.

Although the present invention has been described with reference to the most practical and preferred embodiments, the present invention is not limited to the above disclosed embodiments, but also includes various modifications and equivalents within the scope of the following claims.

According to the present invention, afterimage input by an external light source can be reliably prevented in the optical fingerprint input device.

In addition, the prevention of afterimage input improves the actual fingerprint recognition efficiency.

Claims (7)

An optical fingerprint input device for obtaining a fingerprint image of light reflected by irradiating an internal light source to a fingerprint, An optical path changing unit having a fingerprint input window on which a fingerprint is placed and changing an optical path by reflecting or refracting light; An illumination system including an internal light source for irradiating light of a specific wavelength region among wavelength regions other than a wavelength range of light input from the outside, and controlling the internal light source to irradiate light to the fingerprint input window to make an image of a fingerprint; A filter unit configured to pass light corresponding to a wavelength range of light emitted from the internal light source among light whose optical path is changed by the optical path changing unit; An image sensor unit receiving the light passing through the filter unit and outputting the corresponding electric image signal; And An image processing unit for recognizing a fingerprint pattern by shaping the electrical image signal output from the image sensor unit into a digital signal and processing the image. Optical fingerprint input device comprising a. The method of claim 1, And a lens unit for focusing the light passing through the filter unit and inputting the light to the image sensor unit. The method according to claim 1 or 2, And the internal light source irradiates light in an infrared region having a wavelength longer than that of visible light. The method according to claim 1 or 2, And the internal light source emits blue light, which is a short wavelength region, among visible light. The method according to claim 1 or 2, And the optical path changing unit is a prism. The method according to claim 1 or 2, The filter unit is an optical fingerprint input device, characterized in that the bandpass filter for passing the light corresponding to the wavelength region of the light emitted from the internal light source. The method of claim 6, And said bandpass filter is formed by a combination of a lowpass filter and a highpass filter.