JP2738349B2 - Fingerprint image input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fingerprint collating apparatus for identifying an individual using a fingerprint, which is a collection of sweat glands on the surface of a finger of a human body. The present invention relates to a fingerprint image input device for input, an input method thereof, and a feature point extraction method.

[0002]

2. Description of the Related Art An example of a conventional fingerprint image input device in a fingerprint collating device is disclosed in Japanese Patent Application Laid-Open No. 54-85600.

A large number of fingerprint collation apparatuses of this type pay attention to the difference in reflectance due to the unevenness of the fingerprint and obtain the unevenness of the fingerprint as a grayscale image by receiving the light reflected by the finger. In most cases, the extraction of the feature points used in the matching is performed after the image is taken into a computer or the like.

An example described in JP-A-54-85600 will be described below.

Referring to FIG. 13, a fingerprint image input device in a conventional typical fingerprint collation device projects a light projecting section 131 using white light as a light source and a total reflection condition at a contact surface with a finger. It is composed of a prism 132 that reflects white light incident from the light unit 131 and an image sensor 133 that receives the reflected light from the prism 132 and obtains a fingerprint image.

That is, when a finger is not in contact with the prism 132, the white light incident from the light projecting unit 131 is totally reflected on the upper surface of the prism 132, and the image obtained by the image sensor 133 is a bright image over the entire surface. Becomes When inputting a fingerprint, a finger is pressed against the upper surface of the prism 132.
At this time, since the skin and the prism 132 are in contact with each other at the convex part of the fingerprint, the condition for total reflection is not satisfied, and most of the white light from the light emitting unit 131 is absorbed by the skin and a part of the white light is reflected on the contact surface. Will be done. On the other hand, since the skin and the prism 132 are not in contact with each other in the concave portion of the fingerprint, the total reflection condition is satisfied, and the white light from the light projecting unit 131 is totally reflected by the contact surface and is incident on the image sensor 133. Will be. As a result, the concave portions of the fingerprint are bright and the convex portions are dark, and a fingerprint image with contrast is obtained.

In addition, Kazuharu Yamato, "Trends in Fingerprint Verification Technology and Input / Output Management Security Systems", in the magazine "Video Information (1), Vol. 24, pp. 41-48," issued in 1992.
An article entitled is known.

According to this article, when extracting the position and direction data of an end point of a ridge or a branch point as feature point data of a fingerprint, the fingerprint image is taken into a computer or the like, and the taken fingerprint image is taken. Image processing for thinning and extracting feature points is performed.

[0009]

In this type of conventional fingerprint image input device, a huge amount of image processing is required for feature extraction after the fingerprint image is taken into a computer or the like. For this reason, there is a problem that an extra back-end processor dedicated to image processing must be additionally provided for feature point extraction.

In a conventional fingerprint image input device, white light is used when a finger on a prism is irradiated with white light from a projector and the reflected light is received by an image sensor to obtain a fingerprint image. . The conventional fingerprint image input device has a disadvantage that the fingerprint image tends to be unclear because white light is scattered or chromatic aberration occurs.

Further, since the prism used in the conventional device has a triangular prism shape, the fingerprint image from the prism is not parallel to the image pickup device. For this reason, the conventional device also has a disadvantage that trapezoidal distortion is likely to occur in the fingerprint image.

It is an object of the present invention to provide a fingerprint image input device which has a simplified structure.

It is another object of the present invention to provide a fingerprint image input apparatus and a fingerprint image input method capable of obtaining a clear, high-resolution fingerprint image without distortion.

It is another object of the present invention to provide a fingerprint image input apparatus and a fingerprint image input method capable of obtaining a fingerprint image free of trapezoidal distortion.

Another object of the present invention is to provide a feature point extracting method for extracting a feature point from a change in the intensity of light reflected from a prism.

[0016]

The first device of the present invention comprises:
Scanning means for scanning a laser spot converged to a predetermined size of laser light along one of fingerprint ridges and valleys of a finger placed on a transparent polyhedron (hereinafter, prism); Detecting means for detecting the intensity of reflected laser light reflected from the prism by scanning.

A second apparatus according to the present invention is the first apparatus, and further includes recording means for recording data relating to the intensity of reflected light detected by the detecting means.

According to a third aspect of the present invention, there is provided a scanning device for scanning a laser spot converged to a predetermined size of a laser beam along one of a fingerprint ridge and a valley of a finger placed on a prism. And an extracting means for converting the intensity of the laser light reflected from the prism by the scanning of the scanning means and extracting a characteristic point from the converted electric signal.

A fourth device of the present invention is the third device, and further includes a recording unit that records the characteristic points extracted by the extraction unit.

According to a fifth aspect of the present invention, there is provided a scanning device for scanning a laser spot converged to a predetermined size of a laser beam along one of a fingerprint ridge and a valley of a finger placed on a prism. Means, and data generating means for converting the intensity of the laser light reflected from the prism by scanning by the scanning means and generating image density data from the converted electric signal.

A sixth apparatus according to the present invention is the fifth apparatus, and further includes an extracting unit for extracting a feature point from the data generated by the data generating unit.

A seventh device of the present invention is the sixth device, further comprising a recording unit for recording the feature points extracted by the extraction unit.

An eighth apparatus according to the present invention comprises a lens (3 in FIG. 1) for scanning a laser beam having a predetermined constant wavelength on the optical axis so as to converge into a spot of a predetermined size. A first mirror (4 in FIG. 1) for scanning the laser spot converged by the lens in the main scanning direction on a contact surface of the prism with the finger, and a laser spot converged by the lens with the finger of the prism; A second mirror (5 in FIG. 1) for scanning in the sub-scanning direction on the contact surface, and a light receiving unit (8 in FIG. 1) for receiving reflected light from the prism and converting the reflected light intensity into an electric signal. Generating image density data based on an electric signal from the light receiving unit, forming a fingerprint image from the image density data, and forming the lens and the first and second lenses.
And a controller (9 in FIG. 1) for transmitting a drive control signal for scanning the laser spot in the optical axis direction, the main scanning direction, and the sub-scanning direction by a predetermined number of steps with respect to the mirror.

The ninth apparatus according to the present invention is arranged so that a laser beam having a predetermined wavelength is converged into a spot having a predetermined size substantially equal to the width of a fingerprint ridge or valley. A lens that scans upward (3 in FIG. 1), a first mirror (4 in FIG. 1) that scans the laser spot converged by the lens in the main scanning direction on the contact surface of the prism with the finger,
A second mirror (5 in FIG. 1) that scans the laser spot converged by the lens on the contact surface of the prism with the finger in the sub-scanning direction; A light receiving unit (8 in FIG. 1) for converting the light into an electric signal, a fingerprint ridge is detected based on the electric signal from the light receiving unit, and the lens and the first and second lenses are arranged along the fingerprint ridge. When a drive control signal for scanning the laser spot in the optical axis direction and the main scanning direction and the sub-scanning direction by a predetermined number of steps is transmitted to the mirror, and a feature point is detected by an electric signal from the light receiving unit. And a control unit (9 in FIG. 1) for recording a position on the fingerprint image corresponding to the position on the prism.

A tenth device according to the present invention is characterized in that, in the eighth or ninth device, both the first mirror and the second mirror are galvanometer mirrors.

In a first method of the present invention, a first step of scanning a lens on an optical axis so as to converge a laser beam having a predetermined constant wavelength into a spot of a predetermined size, A second step of moving the laser spot converged by the first mirror to a predetermined initial position in the main scanning direction on the contact surface of the prism with the finger by rotating the first mirror; and reflected light received from the prism. A third step of converting the intensity of the laser spot into an electric signal, generating and recording image density data from the electric signal, and rotating the first mirror to move the laser spot by a predetermined width in the main scanning direction. Moving the laser spot to a predetermined position by rotating the second mirror when scanning in the main scanning direction by the laser spot is completed. The laser is moved by a predetermined width in the sub-scanning direction, and the lens is scanned by a predetermined width to converge the laser to a spot of a predetermined size. When the scanning in the main scanning direction is not completed, the third A fifth step of returning to the step; and a step of returning to the second step when the scanning in the sub-scanning direction by the laser spot is completed and all the operations are completed when the scanning in the sub-scanning direction is not completed. 6 steps.

According to a second method of the present invention, a laser beam having a predetermined wavelength is converged on an optical axis so as to converge into a spot having a predetermined size substantially equal to the width of a fingerprint ridge or a valley. A first step of scanning the lens, and the laser spot converged by the lens is scanned once more by a predetermined width on the contact surface of the prism with the finger by rotating the first and second mirrors. A second step of moving the reflected light in the main scanning direction and the sub-scanning direction, and a third step of converting the intensity of the reflected light received from the prism into an electric signal.
And a drive control for detecting a fingerprint ridge or a valley from the electric signal and scanning the lens and the first and second mirrors so that a laser spot moves in a region near the ridge. A fourth step of transmitting a signal, comparing the electric signal in the ridge and the neighboring area and moving the laser spot along the ridge, and comparing the electric signal in the ridge and the neighboring area; A fifth step of detecting a fingerprint feature point, a sixth step of recording a position on the fingerprint image corresponding to a position on the transparent polyhedron when the feature point is detected, and scanning the laser spot even once. If there is a transparent polyhedron region that has not been processed, a seventh step is returned to the second step.

A third method according to the present invention is the method according to the first or second method, wherein both the first mirror and the second mirror are galvanometer mirrors.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings.

Referring to FIG. 1, in a first embodiment of the present invention, a light emitting section 1 for outputting a laser beam using a semiconductor laser or a light emitting diode as a light source, and a laser beam output from the light emitting section 1 are provided. A lens 2 that scans on the optical axis so as to converge in a minute spot shape, a scanning lens 3 that performs an operation in the optical axis direction according to a control signal and further changes the diameter of the laser light converged by the lens 2, A first galvanometer mirror 4 that performs a rotation operation in accordance with the control signal and reflects the laser light converged by the scanning lens 3 so as to scan in a main scanning direction on a contact surface of the prism 7 with a finger; The laser beam reflected by the first galvanometer mirror 4 is converted into a prism 7
A second galvanometer mirror 5 that reflects light so as to scan further in the sub-scanning direction on the contact surface with the finger; a lens 6 that adjusts the optical path of the laser light reflected by the second galvanometer mirror 5; A spot-shaped laser beam whose optical path has been adjusted by the lens 6 is incident, and the prism 7 reflects the spot-shaped laser beam according to the condition of total reflection at the contact surface with the finger, and reflected light of the laser beam from the prism 7. Receiving the light, detecting the light, converting the light into an electric signal corresponding to the optical intensity of the reflected light, and outputting the electric signal.
The image density data is stored at a predetermined position, a fingerprint ridge portion is detected, and a spot on the scanning lens 3, the first galvanometer mirror 4, and the second galvanometer mirror 5 is detected as the fingerprint ridge. A drive control signal for scanning the laser beam in the optical axis direction, the main scanning direction, and the sub-scanning direction by a predetermined number of steps is transmitted, and the prism 7 when the characteristic point is detected by the electric signal from the light receiving unit 8 is transmitted. A control unit 9 for outputting a control signal for controlling an operation of recording a position on the fingerprint image corresponding to the position, and a display unit 10 for displaying the fingerprint image based on the image density data stored by the control unit 9 And

Next, the operation of the first embodiment of the present invention will be described with reference to FIGS. 1, 2 and 3.

The laser beam output from the light projecting unit 1 is converged by the lens 2 and then enters the scanning lens 3. The scanning lens 3 can change the spot diameter of the laser beam by moving the lens in the optical axis direction according to a control signal output from the control unit 9 as shown in FIG.
It is possible to prevent the spot diameter of the laser beam applied to the prism 7 from changing according to the position in the sub-scanning direction, and to keep the spot diameter constant. The laser light converged by the scanning lens 3 is incident on a first galvanometer mirror 4.
The first galvanometer mirror 4 also scans the laser beam in the main scanning direction according to a control signal output from the control unit 9 shown in FIG. The laser light reflected by the first galvanometer mirror 4 is incident on the second galvanometer mirror 5, and scans the laser light in the sub-scanning direction according to a control signal output from the control unit 9. The laser beam reflected by the second galvanometer mirror 5 has its optical path adjusted by the lens 6 and is applied to the contact surface of the transparent polyhedron with the finger of the isosceles prism 7. At this time, on the contact surface between the prism 7 and the finger, a spot-shaped laser beam is scattered at a portion in contact with the convex portion of the fingerprint because the condition for total reflection is not satisfied. On the other hand, at the contact surface between the prism 7 and the finger,
At the portion in contact with the concave portion of the fingerprint, the spot-like laser light is totally reflected since the condition for total reflection is satisfied.

As described above, in the present invention, the use of laser light as a light source makes it possible to eliminate the scattering or chromatic aberration of white light, which has been a problem in the past, thereby preventing the fingerprint image from becoming unclear. Can be prevented.

Referring to FIGS. 1 and 2, the prism 7
The intensity of the spot-like laser light reflected by the
And converted into an electrical signal. Subsequently, the control unit 9
Is an internal memory 91 which receives an electric signal and stores it as image density data at an address corresponding to the position irradiated by the prism 7.
Write to. When it is determined that one line has been scanned in the main scanning direction, the control unit 9 outputs a control signal to the second galvanometer mirror 5 to move the one line in the sub-scanning direction, and further outputs the first galvanometer. A control signal is output to the mirror 4 so as to scan one line from the initial position in the main scanning direction. At this time, a control signal for moving the lens in the optical axis direction is output to the scanning lens 3 so that the size of the laser spot does not change depending on the position of the laser spot in the sub-scanning direction. By repeating such processing until the end of the sub-scanning direction, two-dimensional scanning of the fingerprint by the spot-like laser light is realized. The reflected light intensity of the laser light stored in the internal memory 91 is displayed on the display unit 10 as an image representing the intensity distribution.

In the present invention, the optical path of the laser beam is
Even if the light is distorted before the light enters the light receiving unit 8, since the reflected light intensity of each point is recorded in the address of the internal memory 91 corresponding to each point on the prism 7, a fingerprint image without trapezoidal distortion is obtained. can get.

The control unit 9 which is a feature of the first embodiment is described.
Will be described with reference to FIGS. 1, 2 and 6. FIG.

Referring to FIG. 1, FIG. 2 and FIG. 6, first, the control unit 9 sends a control signal for moving the scanning lens 3, the first galvanometer mirror 4 and the second galvanometer mirror 5 to the initial position. Then, the laser spot is moved to the initial position of the contact surface of the prism 7 with the finger (FIG. 6, step S61, step S62). Next, the control section 9 receives an electric signal corresponding to the intensity of the reflected light from the prism 7 detected by the light receiving section 8 and writes it as an image density data at a predetermined position in the internal memory 91 (FIG. 6, step S63). . Further, the control unit 9 sends a control signal for moving the first galvanometer mirror 4 in the main scanning direction by one step to the first galvanometer mirror 4, and causes the laser spot to contact the finger of the prism 7 in the main scanning direction. Is moved by one step (FIG. 6, step S64). Here, the control unit 9 determines whether the scanning of the laser beam in the main scanning direction has been completed (FIG. 6, step S65), and if not completed, returns to step S63 to continue the reflected light from the light receiving unit 8. The intensity signal is received and recorded in the internal memory 91 as image density data, and if it is completed, a control signal for moving the second galvanometer mirror 5 in the sub-scanning direction by one step is sent to the second galvanometer mirror 5. ,
The laser beam is moved by one step in the sub-scanning direction (FIG. 6,
Step S66). Further, a control signal for moving the scanning lens 3 in the optical axis direction in accordance with the position of the laser spot on the contact surface of the prism 7 with the finger in the sub-scanning direction is transmitted to the scanning lens 3.
(FIG. 6, step S67). Then, the control unit 9 determines whether the scanning of the laser beam in the sub-scanning direction has been completed (FIG. 6, step S68), and if not completed, returns to step S62 to move the laser spot to the initial position again. The scanning is performed, and if the scanning is completed, all the control operations are terminated.

Next, a second embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, 4, 5, 9, and 10. FIG.

Referring to FIG. 1, FIG. 2 and FIG. 3, the laser beam output from the light projecting unit 1 is converged by the lens 2 and then enters the scanning lens 3. This scanning lens 3
As shown in FIG. 3, the spot diameter of the laser light can be changed by moving the lens in the direction of the optical axis of the lens in accordance with the control signal output from the control unit 9. It is possible to prevent the spot diameter from changing depending on the position in the sub-scanning direction and keep the spot diameter at a constant average fingerprint ridge width. The laser light converged to the width of the fingerprint ridge by the scanning lens 3 is incident on the first galvanometer mirror 4. The first galvanometer mirror 4 also scans the laser beam in the main scanning direction according to a control signal output from the control unit 9. The laser light reflected by the first galvanometer mirror 4 is incident on the second galvanometer mirror 5, and scans the laser light in the sub-scanning direction according to a control signal output from the control unit 9. The laser light reflected by the second galvanometer mirror 5 is
As a result, the light path is adjusted, and the light is irradiated on the contact surface of the isosceles prism 7 which is a transparent polyhedron with the finger. At this time, on the contact surface between the prism 7 and the finger, a spot-shaped laser beam is scattered at a portion in contact with the convex portion of the fingerprint because the condition for total reflection is not satisfied. On the other hand, at the contact surface between the prism 7 and the finger, the portion in contact with the concave portion of the fingerprint satisfies the condition of total reflection, so that the spot-shaped laser light is totally reflected. In addition, the scanning width of the laser spot scanned on the prism 7 is equal to or less than half the laser spot diameter. The intensity of the spot-shaped laser light reflected by the prism 7 is detected by the light receiving unit 8 and converted into an electric signal. Subsequently, the control unit 9 receives the electric signal, and temporarily stores the electric signal as image density data at an address corresponding to the position irradiated by the prism 7.

Referring to FIGS. 1 and 4, when the density data value is the ridge point 12 below the threshold value, the control unit 9 controls the first galvanometer mirror 4, the second galvanometer mirror 5, and the scanning lens 3 to operate. A control signal is sent to scan a laser spot of a fixed size in eight directions around the ridge point 12. At this time, the reflected light intensity of the laser light in each direction is detected by the light receiving unit 8 and converted into an electric signal, and then temporarily stored as image density data at an address corresponding to the position irradiated by the prism 7. The controller 9 determines the ridge direction in which the image density data is minimum and equal to or less than the threshold value from among the eight directions, and scans the laser spot as the next ridge point and in the eight directions around the ridge point. . The above operation is repeated to trace the ridge.
At this time, the point once scanned is not scanned.

Referring to FIG. 5, the relationship between the unscanned point, the scanned point, and the ridge point is shown, where four of the eight directions of scanning around the ridge point 12 are scanned points and the remaining Four directions are scanned.
When tracing to the end point 13 of the ridge 11, at this point, even if the laser spot is scanned in eight directions, there is no direction in which the image density data value becomes lower than the threshold value.

Referring to FIG. 1 and FIG.
Is recorded in the internal memory 91 at an address corresponding to the position irradiated with the laser by the prism 7 with the end point 13 as a feature point. The control unit 9 controls the first galvanometer mirror 4 and the second galvanometer mirror 5 to search for the next ridge point.
Then, a control signal is sent to the scanning lens 3 so as to scan the laser spot, and feature points are extracted. The above operation is performed for the entire area on the prism 7.

The above is a method of extracting an end point. The method of extracting a branch point is such that the relationship between the end point of the fingerprint and the branch point is such that when the density value is inverted, the end point becomes a branch point and the branch point becomes an end point. The ridge branch point is extracted by searching for a point on the valley line where the reflected light intensity at the valley line portion of the fingerprint is larger than the threshold value in the same manner as the case of the ridge line, and extracting the end point. be able to.

Referring to FIGS. 1 and 9, the prism 7
When the image density data value of the address corresponding to the position where the laser is irradiated above is the valley line point 15 which is equal to or greater than the threshold value, the control unit 9 sets the first galvanometer mirror 4 and the second
A control signal is sent to the galvanometer mirror 5 and the scanning lens 3 so as to scan a laser spot of a fixed size in eight directions around the valley point 15. At this time, the reflected light intensity of the laser light in each direction is detected by the light receiving unit 8 and converted into an electric signal, and then temporarily stored as image density data at an address corresponding to the position irradiated by the prism 7.
The controller 9 determines a valley line direction in which the image density data is maximum and equal to or larger than the threshold value from among the eight directions, and scans the laser spot in the eight directions around the valley line point as the next valley line point. . The above operation is repeated to trace the valley line. At this time, the point once scanned is not scanned.

Referring to FIG. 10, the relationship between the unscanned point, the scanned point, and the ridge point is shown. In the eight directions of scanning around the valley point 15, four directions are the scanned points. Four directions are scanned.
When the trace is traced to the end point 16 of the valley line 14, the point becomes the end point 16 because there is no direction in which the image density data value exceeds the threshold value even if the laser spot is scanned in eight directions at this point.

Referring to FIG. 1 and FIG.
Is the address corresponding to the position irradiated with the laser beam by the prism 7 with the end point 16 as the characteristic point of the branch point, and the internal memory 91
To memorize. The control unit 9 sends a control signal to the first galvanometer mirror 4, the second galvanometer mirror 5, and the scanning lens 3 to scan the laser spot in order to search for the next valley line point, and extracts a feature point. Go. The above operation is performed for the entire area on the prism 7.

The operation of the control unit 9 which is a feature of the second embodiment of the present invention will be described with reference to FIGS.
This will be described with reference to FIG.

First, the operation of endpoint extraction will be described.

Referring to FIG. 1 and FIG.
Sends a control signal for moving the scanning lens 3, the first galvanometer mirror 4 and the second galvanometer mirror 5 to the initial position, and moves the laser spot to the initial position of the contact surface of the prism 7 with the finger (FIG. 7. Step S
71). Next, the control unit 9 receives an electric signal corresponding to the intensity of the reflected light from the prism 7 detected by the light receiving unit 8, and temporarily stores the electric signal as image density data (FIG. 7, step S).
72). At this time, the position of the laser spot on the prism 7 is recorded in the internal memory 91 as having been scanned (FIG. 7, step S73). The control unit 9 determines whether or not the image density data value of the intensity of the reflected light from the prism 7 is equal to or less than a threshold value (step S74 in FIG. 7). The process proceeds to the line tracing and feature point extraction processing (FIG. 8), and if not less than the threshold value, it is determined whether or not the next moving point is recorded as scanned in the internal memory 91 (FIG. 7, step S7).
5). If the scanning has been completed, it is determined whether or not the next moving point has been scanned. If not, the control unit 9 sets the scanning lens 3, the first galvanometer mirror 4, and the second
A control signal is sent to move the laser spot of the galvanometer mirror 5 to its moving point (FIG. 7,
Step S76). Then, the control unit 9 determines whether or not scanning at all points of the laser beam has been completed (FIG. 7, step S77), and if not completed, returns to step S72. The control operation ends.

Referring to FIGS. 1 and 8, when the processing shifts to the ridge tracing and feature point extraction processing (FIG. 8), first, the position of the current laser spot is set as the scanning start point of the fingerprint ridge ( FIG. 8, step S81). The control unit 9 includes the scanning lens 3, the first galvanometer mirror 4, and the second
A control signal is sent so that the galvanometer mirror 5 scans a laser spot of a fixed size in eight directions adjacent to the scanning start point (FIG. 8, step S82). Next, the control unit 9 receives electric signals corresponding to the reflected light intensities in eight directions from the prism 7 detected by the light receiving unit 8, and temporarily stores the image signals as image density data in each of the eight directions (FIG. 8). , Step S83). At this time, the positions of the laser spots in eight directions on the prism 7 are determined to have been scanned,
(FIG. 8, step S84). The control unit 9
It is determined whether or not there is a point where the image density data value of the reflected light intensity in eight directions from the prism 7 is minimum and equal to or less than the threshold value (FIG. 8, step S85). If there is a point below, the point is set as the scanning start point (FIG. 8, step S86), and the process returns to step S82. If there is no point at which the image density value is minimum and equal to or less than the threshold value, the current scanning starts. The position of the laser spot on the prism 7 is recorded in the internal memory 91 as a feature point, with the point as an end point (FIG. 8, step S8).
7), and return to step S75 (FIG. 7).

Next, the operation of branch point extraction will be described.

Referring to FIG. 1 and FIG.
Sends a control signal for moving the scanning lens 3, the first galvanometer mirror 4, and the second galvanometer mirror 5 to the initial position, and moves the laser spot to the initial position of the contact surface of the prism 7 with the finger (FIG. 11, step S111). Next, the control unit 9 receives an electric signal corresponding to the reflected light intensity from the prism 7 detected by the light receiving unit 8,
It is temporarily stored as image density data (FIG. 11, step S112). The position of the laser spot on the prism 7 at this time is recorded in the internal memory 91 as having been scanned (step S113 in FIG. 11). The control unit 9 determines whether or not the image density data value of the intensity of the reflected light from the prism 7 is equal to or greater than a threshold (FIG. 11, step S114). The process proceeds to the line tracing and feature point extraction processing (FIG. 12).
If the value is not equal to or larger than the threshold value, it is determined whether or not the next movement point is recorded as scanned in the internal memory 91 (FIG. 1).
1. Step S115). When scanning has been completed, the control unit 9
Determines whether the next moving point has been scanned. If scanning has not been completed, the control unit 9 sends a control signal to move the laser spot to the scanning lens 3, the first galvanometer mirror 4, and the second galvanometer mirror 5 to the moving point (FIG. 11, step S11).
6). Then, the control unit 9 determines whether or not the scanning at all points of the laser beam has been completed (FIG. 11, step S117). If not completed, the process returns to step S112. The control operation ends.

When the processing of FIG. 1 and FIG. 12 is completed and the processing proceeds to the processing of extracting the trace of the valley line and the feature point (FIG. 12), first, the position of the current laser spot is set as the scanning start point of the fingerprint valley line (FIG. 12, step S121). Control unit 9
Sends a control signal so that the scanning lens 3, the first galvanometer mirror 4, and the second galvanometer mirror 5 scan a laser spot of a fixed size in eight directions adjacent to the scanning start point (FIG. 12, step S122).
Next, the control unit 9 receives an electric signal corresponding to the reflected light intensity in eight directions from the prism 7 detected by the light receiving unit 8, and temporarily stores the image signal as image density data in each of the eight directions (FIG. 12, FIG. Step S123). At this time, the positions of the laser spots in the eight directions on the prism 7 are recorded in the internal memory 91 as having been scanned (FIG. 12, step S12).
4). The control unit 9 determines whether or not there is a point where the image density data value of the reflected light intensity in eight directions from the prism 7 is maximum and equal to or more than a threshold value (FIG. 12, step S12).
5) If there is a point where the image density value is maximum and equal to or greater than the threshold value, the point where the image density value is maximum is set as the scanning start point (FIG. 12, step S126), and the process returns to step S122 to return to the image density value. If there is no point where is greater than or equal to the maximum and the threshold value, the current scanning start point is taken as the branch point,
The position of the laser spot on the prism 7 is recorded in the internal memory 91 as a feature point (FIG. 12, step S12).
7), and return to step S115 (FIG. 11).

[0054]

One of the features of the present invention is that a laser spot is scanned along a fingerprint ridge or valley on a prism by a simple control, and a feature point is extracted and recorded from a difference in intensity of light reflected from the prism. Is to do. As a result, according to the present invention, it is not necessary to perform feature point extraction by complicated image processing, and it is not necessary to additionally add a back-end processor dedicated to image processing. In addition, according to the present invention, feature point extraction by image processing that can only be performed by the image processing unit can be performed by the image input unit.

Another feature of the present invention resides in that laser light, which is light of a single wavelength, is focused in a spot shape and all the reflected light intensity from the prism at each irradiation point is detected.
With this feature, the signal per pixel can be increased, and the noise ratio (S / N) to the signal value increases. That is, according to the present invention, the laser beam is converged into a very small spot, the laser spot is two-dimensionally scanned on the contact surface of the prism with the finger, and the image density is adjusted according to the reflected light intensity of each laser spot. By recording the data,
It is possible to obtain a clear image without the adverse effects of scattering and chromatic aberration.

Further, the present invention does not necessarily capture a distorted two-dimensional image with a two-dimensional image pickup device as it is. Since the reflected light intensity of each point is recorded in a memory address of a computer or the like corresponding to the point, the point is not affected by distortion.

As a result, the present invention can obtain a fingerprint image without trapezoidal distortion.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a top view of a part of the embodiment shown in FIG. 1 as viewed from above.

FIG. 3 is a diagram showing a relationship between a laser spot diameter on a prism and a position of a scanning lens.

FIG. 4 is a diagram showing scanning of a feature point of a fingerprint ridge and a laser spot.

FIG. 5 is a diagram showing a scanning direction of a ridge point.

FIG. 6 is a flowchart showing an operation of the control unit 9 in FIG. 1 when an image is input.

FIG. 7 is a flowchart showing an operation of the control unit 9 in FIG. 1 when extracting an end point.

FIG. 8 is a flowchart showing an operation of the control unit 9 in FIG. 1 when extracting an end point.

FIG. 9 is a diagram showing scanning of characteristic points of a fingerprint valley line and a laser spot.

FIG. 10 is a diagram showing a scanning direction of a valley line point.

11 is a flowchart showing the operation of the control unit 9 in FIG. 1 when extracting a branch point.

12 is a flowchart showing the operation of the control unit 9 in FIG. 1 when extracting a branch point.

FIG. 13 is a diagram showing a configuration of a conventional fingerprint image input device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light projecting unit 2 lens 3 scanning lens 4 first galvanometer mirror 5 second galvanometer mirror 6 lens 7 prism 8 light receiving unit 9 control unit 10 display unit 11 ridge 12 ridge point 13 end point 14 valley 15 valley point 16 End line 91 Internal memory

Claims (2)

(57) [Claims] 1. A laser spot obtained by converging a laser beam to a predetermined size onto a finger placed on a transparent polyhedron, and the reflected light intensity of the laser beam from one of ridges and valleys of the fingerprint. Scanning means for scanning along the fingerprint ridge or the valley line by moving the irradiation position of the laser spot on the finger so that the reflected light intensity satisfies a desired condition; A fingerprint image input device, comprising: an extracting unit that extracts a feature point of a fingerprint using a scanning result obtained by the scanning unit. 2. The fingerprint image input device according to claim 1, further comprising a recording unit that records the feature points extracted by the extraction unit.