KR20060117137A - Optical finger print input apparatus and method for determining finger print input on the same - Google Patents

Abstract

An optical fingerprint input device and a fingerprint input determining method thereof are provided to remove input caused from a remaining image by extracting an element performing a complementary role from both images obtained when an internal light source is turned on and off, and discriminating the actual fingerprint input through optimization of the extracted elements. A prism(100) includes a fingerprint input window, and changes an optical path by reflecting or refracting light. A lighting system(110) includes the internal light source and makes the internal light source emit the light to the fingerprint input window. An image sensor(130) outputs an image signal by detecting a fingerprint image through the fingerprint input window. An image processor(140) recognizes a fingerprint pattern by formatting the image signal into a digital signal and processing the digital signal, and discriminates whether the obtained image is the remaining image or not by using the first and second counter value. The first counter value is generated by combining the first and second element respectively extracted from the image when the internal light source is turned on and off.

Description

Optical fingerprint input device and fingerprint input determination method in the device {OPTICAL FINGER PRINT INPUT APPARATUS AND METHOD FOR DETERMINING FINGER PRINT INPUT ON THE SAME}

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 flowchart of a method for determining afterimages in an optical fingerprint input device according to an exemplary embodiment of the present invention.

FIG. 5 is a detailed flowchart of a method of processing an image acquired when the internal light source shown in FIG. 4 is first turned on.

FIG. 6 is a detailed flowchart of a method of processing an image acquired when the internal light source shown in FIG. 4 is turned off.

7 is a diagram illustrating an image when no external light source is input when a fingerprint is input.

8 is a diagram illustrating an image when there is an external light source such as sunlight when a fingerprint is input.

FIG. 9 is a detailed flowchart of a method of processing an image acquired when a second light source is turned on in FIG. 4.

FIG. 10 is a detailed flowchart of a method for determining whether a fingerprint is input shown in FIG. 4.

11 is a diagram illustrating an image when an external light source is continuously turned on.

FIG. 12 is a diagram illustrating an image when an external light source repeats on and off at specific cycles.

13 is a block diagram of an optical fingerprint input device according to an embodiment of the present invention.

The present invention relates to an optical fingerprint recognition device, and more particularly, to an optical fingerprint input device for preventing an afterimage caused by a fingerprint remaining in a fingerprint input window in which an individual's finger fingerprint is in contact, and a fingerprint input determination method in the device. will be.

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. Since the ridge is in contact with the fingerprint input window 9, the light is absorbed without total reflection on 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 avoid the black and white inverted according to the input method of the fingerprint image appearing on the computer monitor, the scattering fingerprint input device is processed by inverting the image 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, at an angle of a specific range from the external light source, not the internal light source. When light is incident, an afterimage of the remaining fingerprint may be detected by the image sensor. When the image sensor detects the 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 extracts elements that complement each other from each image obtained through the flashing of the internal light source and determines the actual fingerprint input through their optimization The present invention provides an optical fingerprint input device for removing an input due to an afterimage and a fingerprint input discrimination method using the device.

Fingerprint input determination method in the optical fingerprint input device according to a feature of the present invention for achieving the above object,

A method for determining the actual fingerprint input in the optical fingerprint input device,

Irradiating an internal light source and acquiring an image; A second step of extracting a first element from the image acquired in the first step; A third step of acquiring an image without irradiating an internal light source; A fourth step of extracting a second element from the image acquired in the third step and generating a first counter value by combining the first element and the second element; Irradiating an internal light source and acquiring an image; A sixth step of extracting a third element from the image obtained in the fifth step and generating a second counter value by combining the first element and the third element; And a seventh step of determining whether the acquired image is an image by an actual fingerprint input using the first counter value generated in the fourth step and the second counter value generated in the sixth step. .

Here, the first element is an edge average that is a value obtained by dividing an edge sum of a specific block unit for an image obtained in the first step by the number of pixels in the block, and the second element is obtained in the third step. An edge average of the specific block unit for the image, wherein the third element is an edge average of the specific block unit for the image obtained in the fifth step.

The fourth step may further include: an eighth step of determining whether the second element is greater than the first element for the specific block; A ninth step of repeating the eighth step for each block constituting the acquired image; And a tenth step of setting the number of blocks in which the second element is larger than the first element as the first counter value.

In addition, the sixth step may include: an eleventh step of determining whether a difference between the third element and the first element is greater than a specific first threshold value for the specific block; A twelfth step of repeating the eleventh step for each block constituting the obtained image; And a thirteenth step of setting the number of blocks in which the difference between the third element and the first element is greater than the first threshold value to the second counter value.

Further, in the seventh step, when the first counter value is smaller than the specific second threshold value and the second counter value is smaller than the specific third threshold value, the acquired image is an image by an actual fingerprint input. It is characterized by determining.

In the seventh step, when the first counter value is greater than or equal to a specific second threshold value or the second counter value is greater than or equal to a specific third threshold value, the acquired image is determined to be an afterimage. .

Here, the specific block unit is characterized in that the 16 pixel × 16 pixel block unit.

In addition, the optical fingerprint input device according to another feature of the present invention,

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, which changes an optical path by reflecting or refracting light; An illumination system including an internal light source and controlling the internal light source to irradiate light to the fingerprint input window to make an image of a fingerprint; An image sensor unit for detecting an image of a fingerprint placed on the fingerprint input window and outputting the image as an electrical image signal; Recognizing a fingerprint pattern by shaping the electrical image signal output from the image sensor unit into a digital signal and image processing, when the first element extracted from the image obtained when the internal light source is irradiated and the internal light source is not irradiated A second counter value is generated by combining the second element extracted from the acquired image, and a second counter value is combined by combining the first element and the third element extracted from the acquired image when the internal light source is irradiated for the second time. An image processing unit for determining whether the acquired image is an input image by a fingerprint by using the first counter value and the second counter value after generating a? And a fingerprint input controller configured to control the illumination system, the image sensor unit, and the image processor, and to remove the image when it is determined that the image determined by the image processor is not an input image by a fingerprint.

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

4 is a flowchart of a method for determining afterimages in an optical fingerprint input device according to an exemplary embodiment of the present invention.

As shown in FIG. 4, the optical fingerprint input apparatus first turns on an internal light source (S10), acquires an image (S12), and performs processing on the acquired image to extract a first element (S14). . Thereafter, the internal light source is turned off (S16), an image is obtained (S18), a process is performed on the obtained image to extract a second element, and then the first counter is formed by combining the first element and the second element. A value iCnt1 is generated (S20). At this time, the image processing extracts a second element from the image acquired when the internal light source is turned off in step S18, and compares the first element with the first counter value iCnt1 by comparison with the first element extracted in step S14. Create

Next, the internal light source is turned on again (S22), an image is obtained (S24), and a third element is extracted by performing processing on the obtained image, and then the second element is combined by combining the first element and the third element. The counter value iCnt2 is generated (S26). At this time, the image processing extracts a third element from the image acquired when the second internal light source is turned on in step S24, and compares the second counter value (by comparison with the first element extracted in step S14). iCnt2).

Finally, the first counter value iCnt1 and the second counter value iCnt2 generated in the image processing steps S20 and S26 are used to determine whether the fingerprint is a real fingerprint input or an afterimage input (S28).

Meanwhile, in operation S14 of an image acquired when the internal light source is first turned on, the image obtained and input in the previous step S12 is divided into blocks of a specific area unit as shown in FIG. 5 (S141). . Herein, a block of a specific area unit may be determined in various ways. In the present embodiment, it is assumed that the area of 16 pixels x 16 pixels is divided into unit blocks.

In this manner, after dividing the input image into units of 16 × 16 blocks (S141), the first block is first selected (S142). Thereafter, the edge average E1n, which is the first element of the selected block, that is, the first block, is calculated (S143). In this case, n corresponds to the block number, and when a 512 × 512 image is divided into 16 × 16 block units, it is a natural number from 1 to 1024.

Hereinafter, the method of calculating the edge average E1n will be described.

In general, the term 'edge' in image processing is an element measuring a change rate or sharpness of an image, and an edge of a pixel may be expressed by [Equation 1].

       When applying Equation 1 to an image, two masks indicated by [Mask 1] and [Mask 2] are used.

[Mask 1]

[Mask 2]

       The two masks extract the rate of change of the x-axis and the rate of change of the y-axis in the image, respectively, and the size of the final edge is expressed by [Equation 2].

의 합이며, 에지 평균은 에지의 합을 블록 내에 있는 화소의 개수로 나눈 값이 된다.Finally, the sum of the edges in the block

The edge average is the sum of the edges divided by the number of pixels in the block.

Therefore, in step S143, the edge average E1n of the block selected according to the edge average calculation method is calculated. Here, n indicated in the edge average E2n represents the n-th block. For example, the edge average of the first block may be represented as E11, and the edge average of the second block may be represented as E12.

On the other hand, the edge average calculation method described above may be implemented according to well-known methods well known to those skilled in the art, an edge average calculation method other than the above-described method may be used.

Next, it is determined whether the selected block is the last block of the input image (S144). If it is not the last block, the next block is selected (S145), and the steps S143 and S144 are repeated. These steps S143, S144, and S145 may be repeated until the selected block becomes a final block, so that an edge average E1n of each of the divided blocks may be calculated for an image obtained when the internal light source is first turned on. .

On the other hand, the processing step (S20) for the image obtained when the internal light source is turned off, as shown in the accompanying FIG. 6, divides the image obtained and input in the previous step (S18) into blocks of a specific area unit (S201). Herein, the blocks of a specific area unit may be determined in various ways as described above, and should be determined in the same way as the division unit determined in the step S14. In this embodiment, the area of 16 pixels × 16 pixels is used as a unit block. Suppose that you divide.

In this manner, after dividing the input image into units of 16 × 16 blocks (S201), the first block is first selected and initialization is performed (S202). This initialization includes setting the first counter value iCnt1, which is the first element to be used in the afterimage determination step S28, to zero.

Next, the edge average E2n, which is the second element of the selected block, that is, the first block, is calculated (S203). The edge average E2n at this time is calculated by the same method as the edge average calculation method described above. In addition, the edge average E2n is an edge average for the nth block, that is, n represents an index for each block. For example, the edge average of the treatment block may be represented as E21, and the edge average of the second block may be represented as E22.

As such, when the edge average E2n of the selected block of the image acquired in the step S18 is calculated, the edge average E2n is the corresponding block of the image obtained when the internal light source first obtained in the step S14 is turned on. It is determined whether or not the edge is larger than the edge average E1n (S204).

If the edge average E2n is larger than the edge average E1n, the first counter value iCnt1 is increased by one (S205), otherwise, the previous first counter value iCnt1 is kept as it is.

Next, it is determined whether the selected block is the last block of the input image (S206). If it is not the last block, the next block is selected (S207), and the steps S203, S204, S205, S206, and S207 are repeated.

These steps (S203, S204, S205, S206, S207) are repeated until the selected block becomes the final block, so that the edge average E2n of the selection block of the image acquired with the internal light source turned off becomes the internal light source. The number of blocks larger than the edge average E1n of the block corresponding to the selection block of the image acquired in this first on state is set in the first counter value iCnt1.

In this manner, the number of blocks estimated as abnormal blocks in the image acquired when the internal light source is turned off is set in the first counter value iCnt1.

This will be described in more detail with reference to FIGS. 7 and 8.

FIG. 7 is a diagram illustrating an image when no external light source is input when a fingerprint is input, and FIG. 8 is a diagram illustrating an image when there is an external light source such as sunlight when a fingerprint is input, respectively. ) Is an image obtained when the first internal light source is turned on, (b) is an image obtained when the internal light source is turned off, and (c) is an image obtained when the second internal light source is turned on.

In FIG. 7B, when there is no external lighting, there is no image input, but when there is external lighting, as shown in FIG. 8B, a considerable amount of video input occurs.

As can be seen from (a) and (b) of FIG. 7 and (a) and (b) of FIG. 8, when an actual fingerprint is input both with and without an external light source, it is acquired when the internal light source is turned off. The image is not clearer than the image acquired when the first internal light source was turned on. That is, the sum of edge averages or gray levels of blocks of an image acquired when the internal light source is turned off is not greater than the sum of edge averages or gray levels of the corresponding blocks of the image acquired when the first internal light source is turned on. Therefore, in step S204 of FIG. 6, the first counter value iCnt1, which is a result value that satisfies the condition of 'edge average E2n> edge average E1n', is the number of abnormal blocks. The more the afterimage condition is intensified.

On the other hand, if the block selected in the step S206 is the final block, the first counter value iCnt1 is stored so that it can be used in the fingerprint input determination step S28, and then the processing step S20 of the image acquired when the internal light source is turned off is Is done.

Meanwhile, the processing step S26 for the image acquired when the internal light source is turned on second is illustrated in FIG. 9 and the processing step S20 for the image obtained when the internal light source is turned off described with reference to FIG. Similar, so briefly.

First, after dividing the image acquired and input at the second time of the internal light source into units of 16 × 16 blocks (S261), the first block is selected and initialization is performed (S262). This initialization includes setting the second counter iCnt2, which is the second element to be used in the afterimage determination step S28, to zero.

Next, an edge average E3n, which is a third element of the selected block, that is, the first block, is calculated (S263), and from the calculated edge average E3n, the image obtained when the internal light source calculated in step S14 is first turned on. It is determined whether the absolute value after subtracting the edge average E1n of the block is greater than the first specific threshold value (S264).

If the absolute value of the edge average E3n minus the edge average E1n is greater than the first threshold value, the second counter value iCnt2 is increased by one (S265), otherwise, the previous second value is increased. Keep the counter value iCnt2.

Next, it is determined whether the selected block is the last block of the input image (S266). If it is not the last block, the next block is selected (S267), and the steps S263, S264, S265, S266, and S267 are repeated.

These steps (S263, S264, S265, S266, S267) are repeated repeatedly until the selected block is the last block, resulting in an internal at the edge mean (E3n) of the selection block of the image acquired with the internal light source turned on second. The number of blocks having a value obtained by subtracting the edge average E1n of the block corresponding to the selection block of the image acquired when the light source is first turned on is set to the second counter value iCnt2.

In this manner, the number of blocks in which the input image is estimated as an afterimage by the external light source is set in the second counter value iCnt1.

This will be described in more detail with reference to FIGS. 7 and 8.

As can be seen from (a) and (c) of FIG. 7 and (a) and (c) of FIG. 8, when the actual fingerprint is input both with and without an external light source, the first internal light source is turned on. There is little change between the acquired image and the acquired image when the second internal light source is turned on. That is, the difference between the sum of edge averages or gray levels of blocks of an image acquired when the second internal light source is turned on and the sum of edge averages or gray levels of corresponding blocks of the image acquired when the first internal light source is turned on are not large. Therefore, in the step S264 of FIG. 7, '| edge average E3n-edge average E1n | The second counter value iCnt2, which is a result value that satisfies the condition of 'first threshold', corresponds to the number of blocks having a large difference in the blocks of the two acquired images, that is, the number of residual blocks by an external light source.

If the block selected in the step S266 is the final block, the second counter value iCnt2 is stored for use in the fingerprint input determination step S28 and the image processing step S26 is acquired when the internal light source is turned on second. Is completed.

Meanwhile, in the step S28 of determining whether the fingerprint is input, whether the fingerprint is input is determined using the first counter value iCnt1 generated in the step S20 and the second counter value iCnt2 generated in the step S26. do.

In the step S28 of determining whether the fingerprint is input, as shown in FIG. 10, first, it is determined whether the first counter value iCnt1 is smaller than the specific second threshold value (S281). That is, it is determined whether the number of abnormal blocks is smaller than the second threshold value.

If it is determined that the first counter value iCnt1 is smaller than the second threshold value, it is determined whether the second counter value iCnt2 is smaller than a specific third threshold value (S282). That is, it is determined whether the number of residual image input blocks by the external light source is smaller than the third threshold value.

If it is determined that the second counter value iCnt2 is smaller than the third threshold value, the second counter value iCnt2 is determined as an image input by an actual fingerprint (S283). That is, when the number of abnormal blocks is also smaller than the second threshold value and the number of residual image input blocks by the external light source is also smaller than the third threshold value, it is determined as an image input by an actual fingerprint.

However, when the first counter value iCnt1 is equal to or greater than the second threshold in step S281, and when the second counter value iCnt2 is equal to or greater than the third threshold in step S282. It is determined that the afterimage input is not an actual fingerprint input (S284). That is, when the number of abnormal blocks is greater than or equal to the second threshold value or the number of residual image input blocks by the external light source is greater than or equal to the third threshold value, it is determined that the residual block is not an actual fingerprint input.

Therefore, if it is determined that the fingerprint input is the actual fingerprint input in step S283, the video is accepted as an input. If it is determined that the residual image input is input in step S284, the video is not accepted as the input.

As described above, when the image input is not a real fingerprint input, the first element extracted from the image acquired when the first internal light source is turned on and the second element extracted from the image obtained when the internal light source is turned off are compared. Generated by a comparison between a first element extracted from an image acquired at the first internal light source or a third element extracted from an image acquired at the second internal light source on, or removed by one counter value iCnt1; It may be removed by the second counter value iCnt2. Accordingly, the first counter value iCnt1 and the second counter value iCnt2 generated by the combination of the first element, the second element, and the third element may be abnormal inputs or afterimage inputs, not actual fingerprint inputs. Play a complementary role in eliminating That is, the first counter value iCnt1 compares the images when the internal light source is on and off to determine an afterimage caused by the continuous inflow of the external light source, and the second counter value iCnt2 compares the images when the on light source is on and off. 1 In order to avoid the counter value iCnt1, the shape of the afterimage that changes the external light source at a specific period is discriminated. This will be described with reference to FIGS. 11 and 12.

FIG. 11 is a view illustrating an image when an external light source is continuously turned on, and FIG. 12 is a view showing an image when the external light source is repeatedly turned on and off at a specific cycle, and FIGS. 11 and 12 respectively. (a) is an image obtained when the first internal light source is turned on, (b) is an image obtained when the internal light source is turned off, and (c) is an image obtained when the second internal light source is turned on.

First, referring to FIG. 11, when an external light source such as sunlight is continuously irradiated, the three images are the same regardless of whether the internal light source is turned on or off. In this case, the acquired image is determined to be an afterimage by the first counter value iCnt1 comparing the (a) and (b) images, but the (a) and (c) images are almost the same and the second counter value is obtained. (iCnt2) makes it difficult to determine afterimages. In this case, the first counter value iCnt1 plays a major role.

On the other hand, referring to Figure 12, the image is acquired when the external light source such as a floor lamp is repeatedly turned on and off irregularly, especially when the cycle of turning on and off the external light source and the cycle of turning on and off the internal light source is the same The afterimage determination is difficult by the first counter value (iCnt1) comparing the images of (a) and (b), but since the images of (a) and (c) are clearly different, the second counter value (iCnt2) It is discriminated by afterimages. In this case, the role of the second counter value iCnt2 is the main factor for removing the afterimage.

As described above, regardless of the external light source, the first counter value iCnt1 and the second counter value iCnt2 complement each other to remove abnormal inputs or various types of afterimage inputs that are not actual fingerprint inputs. Able to know.

13 is a block diagram of an optical fingerprint input device according to an embodiment of the present invention.

As shown in FIG. 13, an optical fingerprint input device according to an embodiment of the present invention includes a prism 100, an illumination system 110, a lens unit 120, an image sensor unit 130, an image processing unit 140, and a fingerprint. The input controller 150 is included.

The illumination system 110 includes an internal light source, for example, a plurality of LEDs arranged in a specific shape, and controls the light by the internal light source to be used for fingerprint input through the prism 100.

The prism 100 may have various forms 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 110 to the fingerprint in contact with the fingerprint input window where the fingerprint is placed. It changes to guide the lens unit 120.

The lens unit 120 focuses the light induced by the prism 100 to be input to the image sensor unit 130.

The image sensor unit 130 includes, for example, a CCD and a CMOS sensor, and outputs a corresponding electric signal according to the amount of light input through the lens unit 120.

The image processor 140 recognizes a fingerprint pattern by shaping the electrical signal output from the image sensor unit 130 into a digital signal and processing the image.

The fingerprint input controller 150 controls the illumination system 110, the image sensor 130, and the image processor 140 to control the operation of the entire fingerprint input device.

The fingerprint input controller 150 controls the illumination system 110 to turn on the internal light source and then controls the image sensor unit 130 to remove the afterimage input according to an embodiment of the present invention so as to acquire a fingerprint image of one frame. The edge average E1n is calculated for each 16 × 16 block unit of the image acquired by the image processor 140.

In addition, the illumination system 110 is controlled to turn off the internal light source, and then the image sensor unit 130 is controlled to acquire a fingerprint image of one frame, and then 16 × 16 of the image acquired through the image processor 140. After the edge average E2n is calculated for each block unit, the first counter value iCnt1 is generated by comparing the calculated edge average E2n and the previously calculated edge average E1n. The first counter value iCnt1 indicates the number of blocks whose edge average E2n is larger than the edge average E1n.

Similarly, after controlling the illumination system 110 to turn on the internal light source for the second time, the image sensor unit 130 is controlled to acquire a fingerprint image of one frame, and 16 × of the image obtained through the image processor 140 is obtained. After calculating the edge average E3n for each of 16 block units, the second counter value iCnt2 is generated by comparing the calculated edge average E3n with the previously calculated edge average E1n. The second counter value iCnt2 represents the number of blocks in which the absolute value of the edge average E3n minus the edge average E1n is larger than the first threshold value.

Finally, the fingerprint input controller 150 determines whether the input image remains after using the generated first counter value iCnt1 and the second counter value iCnt2. That is, when the first counter value iCnt1 is smaller than the second threshold value and the second counter value iCnt2 is smaller than the third threshold value, the fingerprint input controller 150 converts the input image into an input image by an actual fingerprint. It is determined and accepted.

Therefore, when the first counter value iCnt1 is equal to or greater than the second threshold value or the second counter value iCnt2 is equal to or greater than the third threshold value, the input image is removed without determining and accepting the input image due to the afterimage.

Meanwhile, in the above, the image processor 140 and the fingerprint input controller 150 are separated and described as separate blocks, but the technical scope of the present invention is not limited thereto, and the image processor 140 and the fingerprint input controller 150 are described. Can also be present together in one block.

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, it is possible to reliably discriminate and remove an abnormal input image or an afterimage input by an external light source in the optical fingerprint input device. In addition, it is possible to prevent the wrong input due to afterimages can greatly improve the security.

Claims (13)

In the optical fingerprint input device to determine the actual fingerprint input, Irradiating an internal light source and acquiring an image; A second step of extracting a first element from the image acquired in the first step; A third step of acquiring an image without irradiating an internal light source; A fourth step of extracting a second element from the image acquired in the third step and generating a first counter value by combining the first element and the second element; Irradiating an internal light source and acquiring an image; A sixth step of extracting a third element from the image obtained in the fifth step and generating a second counter value by combining the first element and the third element; And A seventh step of determining whether the acquired image is an image by an actual fingerprint input using the first counter value generated in the fourth step and the second counter value generated in the sixth step Fingerprint input determination method in an optical fingerprint input device comprising a. The method of claim 1, The first element is an edge average that is a value obtained by dividing an edge sum of a specific block unit for the image obtained in the first step by the number of pixels in the block, The second element is an edge average of the specific block unit for the image obtained in the third step, The third element is an edge average of the specific block unit for the image obtained in the fifth step. A fingerprint input discrimination method in an optical fingerprint input device, characterized in that. The method of claim 1, The fourth step, An eighth step of determining whether the second element is greater than the first element for the specific block; A ninth step of repeating the eighth step for each block constituting the acquired image; And A tenth step of setting the number of blocks in which the second element is larger than the first element as the first counter value Fingerprint input determination method in an optical fingerprint input device comprising a. The method of claim 1, The sixth step, An eleventh step of determining whether a difference between the third element and the first element is greater than a specific first threshold value for the specific block; A twelfth step of repeating the eleventh step for each block constituting the obtained image; And A thirteenth step of setting the number of blocks in which the difference between the third element and the first element is greater than the first threshold value to the second counter value; Fingerprint input determination method in an optical fingerprint input device comprising a. The method according to any one of claims 1 to 4, In the seventh step, when the first counter value is smaller than the specific second threshold value and the second counter value is smaller than the specific third threshold value, determining that the acquired image is an image by an actual fingerprint input. A fingerprint input discrimination method in an optical fingerprint input device, characterized in that. The method according to any one of claims 1 to 4, In the seventh step, when the first counter value is greater than or equal to a specific second threshold value, or when the second counter value is greater than or equal to a specific third threshold value, the acquired fingerprint is determined to be an afterimage. Fingerprint input determination method in input device. The method according to any one of claims 2 to 4, And the specific block unit is a 16 pixel × 16 pixel block unit. 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, which changes an optical path by reflecting or refracting light; An illumination system including an internal light source and controlling the internal light source to irradiate light to the fingerprint input window to make an image of a fingerprint; An image sensor unit for detecting an image of a fingerprint placed on the fingerprint input window and outputting the image as an electrical image signal; Recognizing a fingerprint pattern by shaping the electrical image signal output from the image sensor unit into a digital signal and image processing, when the first element extracted from the image obtained when the internal light source is irradiated and the internal light source is not irradiated A second counter value is generated by combining the second element extracted from the acquired image, and a second counter value is combined by combining the first element and the third element extracted from the acquired image when the internal light source is irradiated for the second time. An image processing unit for determining whether the acquired image is an input image by a fingerprint by using the first counter value and the second counter value after generating a? And The fingerprint input control unit controls the illumination system, the image sensor unit, and the image processor, and controls to remove the image when it is determined that the image determined by the image processor is not an input image by a fingerprint. Optical fingerprint input device comprising a. The method of claim 8, The first element is an edge average that is a value obtained by dividing an edge sum of a specific block unit for the image obtained in the first step by the number of pixels in the block, The second element is an edge average of the specific block unit for the image obtained in the third step, The third element is an edge average of the specific block unit for the image obtained in the fifth step. Optical fingerprint input device, characterized in that. The method of claim 8, The image processor After comparing whether the second element is larger than the first element with respect to each block constituting the obtained image, setting the number of blocks in which the second element is larger than the first element as the first counter value, After comparing whether the difference between the third element and the first element is greater than a first threshold value for each block of the acquired image, the difference between the third element and the first element is equal to the first threshold. Setting the number of blocks larger than a value to the second counter value Optical fingerprint input device, characterized in that. The method according to any one of claims 8 to 10, The image processor determines that the acquired image is an image by an actual fingerprint input when the first counter value is smaller than a specific second threshold value and the second counter value is smaller than a specific third threshold value. Optical fingerprint input device made with. The method according to any one of claims 8 to 10, The image processor may determine that the acquired image is an afterimage when the first counter value is greater than or equal to a specific second threshold value or the second counter value is greater than or equal to a specific third threshold value. . The method according to claim 9 or 10, And the specific block unit is a 16 pixel × 16 pixel block unit.

Images