JPH0962828A - Fingerprint picture thinning processor and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To thin a fingerprint ridge at high speed without executing a complicated picture processing. SOLUTION: The laser beams of wavelengths which are mutually different are converged in different large and small spot forms by lenses 2 and 4. Then, the laser beams are converged on the same optical axis by a half mirror 5. Then, a finger on a prism 11 is irradiated with a laser beam by a galvanometer mirror 7 scanning the laser beam in a main scanning direction and a stepping motor 8 scanning the laser beam in an auxiliary scanning direction, and reflected light is divided into two by a half mirror 12. The reflected light of the respective wavelengths is converted into electric signals by band pass filters 13 and 15 in light receiving parts 14 and 15. The thinning part of the fingerprint ridge is detected from the ratio of the two electric signals so as to record it.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fingerprint matching apparatus and method 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 thinning processing device for inputting to a computer or the like and a method thereof.

[0001]

2. Description of the Related Art Thinning of fingerprint ridges used in conventional fingerprint matching focuses on differences in reflectance due to fingerprints, and receives light reflected by a finger to obtain a fingerprint as a grayscale image. In most cases, this was done after being imported to a computer or the like.

Referring to FIG. 10, a fingerprint image input device in a conventional typical fingerprint collating device includes a light projecting unit 101 using white light as a light source and a light projecting unit 101 which satisfies a condition of total reflection on a contact surface with a finger. It is composed of a prism 102 that reflects white light incident from the light unit 101, and an image pickup device 103 that receives the reflected light from the prism 102 and obtains a fingerprint image (Japanese Patent Laid-Open No. 54-85600).

That is, when a finger is not in contact with the prism 102, the white light incident from the light projecting unit 101 is totally reflected on the upper surface of the prism 102, and the image obtained by the image sensor 103 is a bright image over the entire surface. . When a fingerprint is input, a finger is pressed against the upper surface of the prism 102.
At this time, since the skin and the prism 102 are in contact with each other at the ridge portion of the fingerprint, the total reflection condition is not satisfied, and most of the white light from the light emitting unit 101 is absorbed by the skin, and a part of the white light is absorbed by the contact surface. It will be reflected. On the other hand, since the skin and the prism 102 are not in contact with each other at the valley of the fingerprint,
The total reflection condition is satisfied, and the white light from the light projecting unit 1 is totally reflected by the contact surface and is incident on the image sensor 103. As a result, the valley portion of the fingerprint is bright and the ridge portion is dark, so that a fingerprint image with contrast can be obtained.

Furthermore, when thinning fingerprint ridges, a fingerprint image obtained by the fingerprint image input device is taken into a computer or the like, a threshold is determined, the image is binarized, and a mask is used. A method of shaving ridges one pixel at a time from both ends by scanning to make a one-pixel core line,
Thinning is performed by image processing such as a method of obtaining a valley thin line by tracking the direction in which the density of the valley between ridges is minimum. This prior art is described in, for example, "Ichiharu Yamato:"
Trends in Fingerprint Verification Technology and Access Control Security Systems ", Video Information (I), Vol. 24, 1992.

[0005]

In the above-described fingerprint ridge thinning processing by the conventional fingerprint image input apparatus, a back-end processor dedicated to image processing is additionally provided in order to reduce the time required for fingerprint ridge thinning. There is a problem that must be done. This is because an enormous amount of image processing is required for thinning the ridges after the fingerprint image is taken into a computer or the like, and a dedicated processor is required to reduce the time required for thinning the fingerprint ridges.

The object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to improve the characteristics of a fingerprint image thinning device and simplify the device configuration. That is, when thinning fingerprint ridges, laser beams of two types of wavelengths are focused into large and small spots, respectively, and the laser spot is two-dimensionally scanned on the contact surface of the prism with the finger. Another object of the present invention is to thin the fingerprint ridges at high speed without executing complicated image processing by a back-end processor dedicated to image processing by calculating the ratio of the reflected light intensity.

[0007]

In order to solve the above-mentioned problems, a fingerprint image thinning apparatus according to the present invention comprises a plurality of laser light projecting means for generating laser lights having mutually different wavelengths, and a plurality of laser light projecting means. A first half mirror for converging the laser light on the same optical axis, a first surface, a second surface, and a third surface, and receiving the laser light from the half mirror on the first surface. A prism that reflects only the valley of the fingerprint of the finger placed on the second surface through the third surface, and a second half mirror that separates the laser light from the third surface of the prism. A plurality of laser light receiving means for passing laser lights of different wavelengths from each other with respect to the laser light separated by the second half mirror; and a ridge of the fingerprint according to the intensity of the light received by the laser light receiving means. Detect thin line part of And a stage.

Further, another fingerprint image thinning apparatus according to the present invention comprises first and second laser beam projecting means for generating laser beams of mutually different wavelengths, and these first and second laser beam projecting means. First focusing each of the laser light from the means
And a second lens; a first half mirror for converging the laser beams from the first and second lenses on the same optical axis; and a movable half-mirror in the direction of the laser beam path from the half mirror. A scanning system unit for reflecting the laser light so as to scan in the horizontal direction, and a first surface, a second surface, and a third surface, the laser light from the scanning system unit being applied to the first surface. A prism that reflects only the valley portion of the fingerprint of the finger placed on the second surface through the third surface, and a prism that separates the laser light from the third surface of the prism into two. Two half mirrors, a plurality of laser light receiving means for passing laser lights of different wavelengths from each other with respect to the laser light separated by the second half mirror, and the laser light receiving means according to the intensity of light received by these laser light receiving means. Fingerprint And means for detecting the fine line portions of the line.

Further, in another fingerprint image thinning apparatus according to the present invention, the scanning system unit includes a galvanometer mirror.

Further, another fingerprint image thinning processing method of the present invention is characterized in that first and second laser beam projecting means for generating laser beams of mutually different wavelengths, and the first and second laser beam projecting means are provided. A first lens and a second lens that respectively focus laser light from the optical unit; a first half mirror that focuses laser light from these first and second lenses on the same optical axis; A scanning unit movable in the direction of the laser beam path and reflecting the laser beam from the half mirror so as to scan in the horizontal direction; and a scanning system having a first surface, a second surface, and a third surface. A prism that receives a laser beam from a unit on the first surface and reflects only the valley portion of the fingerprint of the finger placed on the second surface through the third surface; and the third surface of the prism. Two laser beams from the surface A second half mirror to be separated, a plurality of laser light receiving means for passing laser lights of different wavelengths from each other with respect to the laser light separated by the second half mirror, and an intensity of light received by the laser light receiving means. Means for detecting a thin line portion of a ridge of the fingerprint in response to the first lens, wherein the first lens focuses the laser light from the first laser light projecting means by the first lens. Step, a second step of converging the laser light from the second laser light projecting means by the second lens, and laser light from the first and second lenses by the first half mirror A third step of converging the laser beam on the same optical axis, a fourth step of moving the laser beam condensed by the first half mirror in the horizontal direction by the scanning system unit, A fifth step of separating the reflected light from the prism into two, a sixth step of transmitting a first wavelength of one of the reflected lights separated by the half mirror, and a separation by the half mirror The seventh of the other reflected light that transmits the second wavelength
An eighth step of converting the intensity of the reflected light from the laser light receiving means into an electric signal, and a ninth step of detecting a thinned portion of a fingerprint ridge from the ratio of the two electric signals. A tenth step of recording a position on the second surface of the prism when the thinning portion is detected;
A first means for horizontally moving the laser light focused by the first half mirror by the scanning system unit;
Step 1: moving the scanning system unit in the direction of the laser beam path when the scanning in the horizontal direction is completed by the scanning system unit, and returning to the eighth step when the scanning in the horizontal direction is not completed. A thirteenth step, in which all operations are terminated when the scanning in the laser beam path direction is completed by the scanning system unit, and the process returns to the fourth step when the scanning in the laser beam path direction is not terminated. And

Further, in another fingerprint image thinning method according to the present invention, the scanning system unit includes a galvanometer mirror.

According to another fingerprint image thinning apparatus of the present invention, a first lens for focusing a laser beam having a predetermined constant first wavelength into a spot of a predetermined size, and a predetermined lens are provided. A second lens for focusing laser light having a constant second wavelength into a spot of a predetermined size;
A half mirror for converging the respective laser beams converged by the second lens and the second lens on the same optical axis, and a laser spot condensed by the half mirror on a contact surface of the transparent polyhedron with a finger. A mirror that scans in the scanning direction, a stepping motor that scans the laser spot focused by the half mirror on the contact surface of the transparent polyhedron with the finger in the sub-scanning direction, and two reflected lights from the transparent polyhedron A half-mirror, a first band-pass filter transmitting a first wavelength of the one reflected light separated by the half mirror, and a first band-pass filter of the other reflected light separated by the half mirror. A second band-pass filter that transmits two wavelengths, a first light-receiving unit that receives reflected light from the first band-pass filter, and converts the reflected light intensity into an electric signal; Receiving reflected light from the serial second bandpass filter, a second to convert the reflected light intensity into an electrical signal
A light receiving portion, and a thin line portion of a fingerprint ridge is determined by calculating an electric signal from the first light receiving portion and the second light receiving portion, and a fingerprint ridge thinned image is formed from the calculation result. A control unit for transmitting a drive control signal for causing the laser spot to scan the mirror and the stepping motor in the main scanning direction and the sub-scanning direction by a predetermined number of steps, respectively.

In another fingerprint image thinning apparatus according to the present invention, the mirror is a galvanometer mirror.

Further, another fingerprint image thinning method according to the present invention includes a first step of focusing a laser beam having a predetermined constant first wavelength into a spot having a predetermined size;
A second step of converging laser light having a predetermined constant second wavelength into a spot of a predetermined size, and the respective laser lights converged by the first lens and the second lens being the same. A third step of condensing the light on the optical axis, and rotating the laser spot condensed by the half mirror to a predetermined initial position in the main scanning direction on the contact surface of the transparent polyhedron with the finger. A fourth step of moving, a fifth step of separating the reflected light from the transparent polyhedron into two, and a sixth step of transmitting a first wavelength of one of the reflected lights separated by the half mirror. And a seventh step of transmitting a second wavelength of the one reflected light separated by the half mirror, and converting the intensity of the reflected light from the first bandpass filter into an electric signal. Eighth A step, a ninth step of converting the intensity of the reflected light from the second bandpass filter into an electric signal, and a tenth step of detecting the thinning portion of the fingerprint ridge from the ratio of the two electric signals. And an eleventh step of recording the position on the fingerprint image corresponding to the position on the transparent polyhedron when the thinning portion is detected; and by rotating the mirror, the laser spot is mainly moved by a predetermined width. A twelfth step of moving in the scanning direction, and when the scanning in the main scanning direction by the laser spot is completed, the laser spot is moved in the sub-scanning direction by a predetermined width by a stepping motor to scan in the main scanning direction. 13th step of returning to the 8th step when not completed, and all operations when scanning in the sub-scanning direction by the laser spot is completed Finished, and a fourteenth step of returning to the fourth step when not finished scanning the sub-scanning direction.

In another fingerprint image thinning method according to the present invention, the mirror is a galvanometer mirror.

In the fingerprint image thinning processing apparatus of the present invention, two kinds of laser light having different wavelengths are focused by the first lens and the second lens into different large and small spots, respectively, and the two laser lights are made by the half mirror. Are focused on the same optical axis and a finger on the prism is irradiated with the laser by a mirror that scans the laser light in the main scanning direction and a stepping motor that scans the laser light in the sub scanning direction. Then, the reflected light is split into two by a half mirror, and the reflected light of each wavelength is separated by a first band-pass filter and a second band-pass filter that transmit only one of the two types of laser light. A light-receiving unit converts the signal into an electric signal, detects and records the thin line portion of the fingerprint ridge based on the ratio of each electric signal, and scans the laser in the main scanning direction to move the laser spot to the next irradiation point. A drive signal is sent from the control unit to a stepping motor that scans the laser in the sub-scanning direction. Therefore, it is not necessary to perform thinning of fingerprint ridges by complicated image processing, and thinning can be performed at high speed without an extra back-end processor dedicated to image processing.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a fingerprint image thinning apparatus according to the present invention will be described in detail with reference to the drawings.

Referring to FIG. 1, a fingerprint image thinning processing apparatus according to an embodiment of the present invention includes
A light projecting unit 1 that outputs a laser beam of a first wavelength using an ED or the like as a light source, a lens 2 that focuses the laser beam output from the light projecting unit 1 into a minute spot, and a laser beam of a second wavelength. And a lens 4 for focusing the laser light output from the light emitting unit 3 to a size about the width of a fingerprint ridge.
A half mirror 5 for condensing the respective laser beams focused by the lens 2 and the lens 4 on the same optical axis;
A mirror 6 for reflecting the laser light condensed by the half mirror 5, and a galvanometer mirror 7 for rotating the laser light according to a control signal and reflecting the laser light reflected by the mirror 6 so as to scan in the main scanning direction. , A lens 9 for adjusting the optical path of the laser light reflected by the galvanometer mirror 7.
And a mirror 10 for reflecting the spot-shaped laser light whose optical path has been adjusted by the lens 9 and a scanning system unit including the mirror 6, the galvanometer mirror 7, the lens 9 and the mirror 10 are moved in the sub-scanning direction according to the control signal. And a stepping motor 8 for causing a spot-shaped laser beam reflected by the mirror 10 to enter and an isosceles prism 11 which is a transparent polyhedron reflecting the spot-shaped laser beam according to a total reflection condition on a contact surface with a finger. A half mirror 12 that separates the reflected laser light from the prism 11 into two, a band-pass filter 15 that transmits a first wavelength of one of the reflected lights separated by the half mirror 12, and a half mirror 12. Of the other reflected light transmitted through the band-pass filter 13 and the band-pass filter 15 transmitting the second wavelength. The reflected light is received with a receiving unit 16 for converting the reflected light intensity into an electrical signal, a band-pass filter 1
A light receiving unit 14 for receiving the reflected light transmitted from the light receiving unit 3 and converting the intensity of the reflected light into an electric signal;
The thin line portion of the fingerprint ridge is determined by calculating the electric signal from the memory 6 and a fingerprint ridge thin line image is formed from the calculation result, and the fingerprint thin line portion data is stored at a predetermined position in the internal memory 171. A control unit 17 for outputting control signals for controlling the operations of the galvanometer mirror 7 and the stepping motor 8, and a display unit 1 for displaying a fingerprint thin line image based on the image density data stored by the control unit 17
8 and. Here, the main scanning direction is, for example, a laser beam direction, and the sub-scanning direction is, for example, a horizontal direction.

Next, the operation of the embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIGS.

Referring to FIG. 3, the laser beam of the first wavelength output from the light projecting unit 1 is focused by a lens 2 on a prism 11 which is a transparent polyhedron so as to form a minute spot. The laser light of the second wavelength output from the light projecting unit 3 is focused by the lens 4 on the prism 11 so as to have a width of about a fingerprint ridge. These two laser beams are
The light is condensed on the same optical axis by the half mirror 5 and is irradiated on the same point on the prism 11.

Referring to FIG. 1, a laser beam condensed on the same optical axis is applied to a galvanometer mirror 7 by a mirror 6.
Is incident on. The galvanometer mirror 7 scans a laser beam in the main scanning direction according to a control signal output from the control unit 17. The optical path of the laser light reflected by the galvanometer mirror 7 is adjusted by the lens 9, and the laser light is applied to the contact surface of the prism 11 with the finger. At this time, on the contact surface between the prism 11 and the finger, the portion in contact with the ridge portion of the fingerprint does not satisfy the condition of total reflection, so that the spot-shaped laser light is scattered. On the other hand, on the contact surface between the prism 11 and the finger, the portion in contact with the valley portion of the fingerprint satisfies the condition of total reflection, so that the spot-shaped laser light is totally reflected.

Referring to FIG. 4, the laser light reflected by the prism 11 is split into two by the half mirror 12, and one of the split reflected lights is the laser light emitted from the minute spot having the first wavelength. The reflected light is transmitted by the bandpass filter 15, and the reflected light by the irradiation laser light of the fingerprint ridge width of the second wavelength of the other reflected light is transmitted by the bandpass filter 13. The intensity of the second laser light from the bandpass filter 13 is detected by the light receiving unit 14 and converted into an electric signal.

Referring to FIG. 7, when the laser light having the fingerprint ridge width does not completely overlap the ridge 23 as in the case of the spot 22, the reflected light intensity becomes equal to or less than the threshold value. Instead, the laser light is scanned to the next point. On the other hand, when the ridge 23 and the laser beam overlap as in the case of the spot 20, the reflected light intensity becomes equal to or higher than the threshold value, and the thin line portion detection processing is subsequently performed. The control unit 17 calculates the reflected light intensity ratio between the fingerprint ridge width spot 20 and the small-diameter spot 19 in the thin line portion detection processing, and when the intensity ratio falls within a certain range, identifies this point as the fingerprint ridge thin line portion. The data of the fingerprint ridge fine line portion is recorded in the internal memory 171 at an address corresponding to the position irradiated by the prism 11.
When it is determined that one line has been scanned in the main scanning direction, the control unit 17 moves one line in the sub-scanning direction with respect to the stepping motor 8 for driving the optical system unit in the sub-scanning direction. Output a control signal.
Here, the optical system unit includes a mirror 6, a galvanometer mirror 7, a lens 9, and a mirror 10. Then, the control signal is further output to the galvanometer mirror 7 so as to scan one line in the main scanning direction from the initial position. 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 performed.

The fingerprint ridge thin line recorded in the internal memory 171 is displayed as an image on the display unit 18. That is, referring to FIG. 5 and FIG. 6, the reflected light intensity ratio at the position of the laser spot 111 irradiated with the laser light is controlled by the control unit 1.
7, the pixel 181 is determined as to whether or not it is a thin line portion, recorded, and displayed on the display unit 18.

The relationship between the reflected light intensity ratio and the thin line portion according to the embodiment of the present invention will be described with reference to FIG.

FIG. 8A shows the distribution of reflected light when a laser spot having the second wavelength and a large fingerprint ridge width is applied to the contact surface between the prism 11 and the finger. One pixel of the ridge image has a distribution that is averaged by pixels in a range as large as the ridge width around the pixel, and the fingerprint ridge image is a blurred image. FIG. 8B shows a reflected light intensity distribution when the contact surface between the prism 11 and the finger is irradiated with the minute laser spot having the first wavelength, and this distribution is the same as the fingerprint ridge image. . FIG. 8C shows the distribution of the reflected light intensity ratios of FIGS. 8A and 8B. 8 (a), 8 (b), 8 (c)
Are aligned, but this irradiates the prism 11 so that large and small laser spots are focused on the same optical axis,
This is because the reflected light intensity at the same position is simultaneously detected for the first wavelength and the second wavelength corresponding to the large and small laser spots. When detecting fingerprint ridge fine line,
First, the reflected light intensity of the laser spot having the size of the fingerprint ridge is detected, and it is determined whether the reflected light intensity is equal to or greater than the threshold value shown in FIG. The reason why the ridge portion is detected at a spot whose laser spot diameter is as large as the fingerprint ridge width is that a small spot diameter is affected by the prism 11 and small dust on the finger. This is because, if the ridge portion is detected based on the diameter, an average reflected light intensity which is not affected by the minute area can be detected. Next, the ratio between the reflected light intensity equal to or higher than the threshold value in FIG. 8A and the reflected light intensity corresponding to the same position in FIG. 8B is calculated. As shown in FIG. 8C, since the intensity ratio of the thin line portion at the center of the ridge falls within a certain range, a point within the range is defined as the fingerprint ridge thin line portion.

Next, the operation of the control unit 17 which is a feature of the embodiment will be described with reference to the drawings.

Referring to FIG. 9, the control unit 17 sends a control signal for moving the galvanometer mirror 7 to the initial position to the galvanometer mirror 7, and moves the laser spot to the initial position on the contact surface of the prism 11 with the finger ( Step S91). Next, the control unit 17 receives an electric signal corresponding to the reflected light intensity of the second wavelength from the prism 11 detected by the light receiving unit 14 and determines whether the value is equal to or greater than the threshold value (step S92). If not more than the threshold value, step S9
5 and the ratio between the signal from the light receiving unit 14 and the value of the electric signal corresponding to the intensity of the reflected light of the first wavelength from the prism 11 when the threshold value or more is obtained. (Step S93), and if it is out of the range, the process branches to step S95. If it is in the range, the position of the current laser spot is recorded as a fingerprint ridge thin line portion (step S93).
94). Then, the control unit 17 sends a control signal for moving the galvanometer mirror 7 in the main scanning direction by one step to the galvanometer mirror 7 and moves the laser spot by one step in the main scanning direction on the contact surface of the prism 11 with the finger ( Step S95). Here, the control unit 17 determines whether the scanning in the main scanning direction of the laser beam has been completed (step S96), and if not completed, returns to step S92 to continue detecting the fingerprint ridge thin line portion. If it has been completed, a control signal for moving the stepping motor 8 in the sub-scanning direction by one step is sent to the stepping motor 8, and the laser beam is moved by one step in the sub-scanning direction (step S97). Then, the control unit 17 determines whether the scanning in the sub-scanning direction of the laser beam has been completed (step S98).
Returning to 91, the laser spot is again moved to the initial position for scanning, and if it has been completed, all control operations are completed.

As described above, according to the fingerprint image thinning processing apparatus according to one embodiment of the present invention, the thin line of the fingerprint ridge can be easily obtained by calculating the reflected light intensity ratio of the two differently sized laser beams. Can be performed.

[0030]

As is apparent from the above description, according to the present invention, thinning processing of fingerprint ridges by complicated image processing can be reduced, processing time for thinning can be shortened, and image processing can be shortened. The configuration of the processing unit can be simplified.

That is, when thinning fingerprint ridges,
By converging the laser light of the two wavelengths into large and small spots respectively, scanning the laser spot two-dimensionally on the contact surface of the prism with the finger, and calculating the ratio of the reflected light intensity for each laser spot, Fingerprint ridge thinning by complex image processing performed by the image processing unit can be performed at high speed by the image input unit.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of an embodiment of a fingerprint image thinning processing apparatus according to the present invention.

FIG. 2 is a partial top view of one embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between spot sizes when a prism is irradiated with two irradiation laser beams.

FIG. 4 is a diagram illustrating a correspondence relationship between two reflected laser beams and a light receiving unit that detects the two reflected laser beams.

FIG. 5 is a diagram illustrating a scanning order of laser spots.

FIG. 6 is a diagram illustrating a correspondence relationship between a laser spot and a pixel of a display unit.

FIG. 7 is a diagram showing a relationship between large and small laser spots irradiated on a ridge and thinning.

FIG. 8 is a diagram illustrating a relationship between a reflected light intensity ratio of a large and small laser spot and a thin line portion.

FIG. 9 is a flowchart illustrating an operation of the control unit when thinning a fingerprint ridge.

FIG. 10 is a diagram illustrating a configuration of a conventional fingerprint image thinning apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light emitting unit 2 lens 3 light emitting unit 4 lens 5 half mirror 6 mirror 7 galvanometer mirror 8 stepping motor 9 lens 10 mirror 11 prism 12 half mirror 13 bandpass filter 14 light receiving unit 15 bandpass filter 16 light receiving unit 17 control unit 171 Internal memory 18 Display unit 19-22 Spot 23 Ridge

Claims (5)

[Claims] 1. A plurality of laser light projecting means for generating laser light having different wavelengths from each other, a first half mirror for converging laser light from these laser light generating means on the same optical axis, Having a surface, a second surface, and a third surface, receiving the laser beam from the half mirror on the first surface, and setting only the valley portion of the fingerprint of the finger placed on the second surface. A prism that reflects through the third surface, a second half mirror that separates the laser light from the third surface of the prism, and laser light that has different wavelengths for the laser light separated by the second half mirror. A plurality of laser light receiving means for transmitting light, and means for detecting a thin line portion of a ridge of the fingerprint according to the intensity of light received by the laser light receiving means. . 2. First and second laser beam projecting means for generating laser beams having different wavelengths from each other, and first and second laser beam projecting means for converging the laser beams from the first and second laser beam projecting devices, respectively. A second lens; a first half mirror for converging the laser beams from the first and second lenses on the same optical axis; a movable halfway mirror in the direction of the laser beam path from the half mirror; A scanning unit for reflecting the laser light so as to scan in the horizontal direction, a first surface, a second surface, and a third surface, the first surface receiving the laser light from the scanning system unit; A prism that reflects only the valley portion of the fingerprint of the finger placed on the second surface through the third surface, and a second that separates the laser light from the third surface of the prism into two. Half mirror and this second A plurality of laser light receiving means for transmitting laser lights of different wavelengths from each other with respect to the laser light separated by the half mirror, and detecting a thin line portion of the ridge of the fingerprint according to the intensity of the light received by the laser light receiving means A fingerprint image thinning processing apparatus. 3. The fingerprint image thinning processing apparatus according to claim 2, wherein the scanning system unit includes a galvanometer mirror. 4. First and second laser beam projecting means for generating laser beams of different wavelengths from each other, and first and second laser beam projecting means for focusing the laser beams from the first and second laser beam projecting devices, respectively. A second lens; a first half mirror for converging the laser beams from the first and second lenses on the same optical axis; a movable halfway mirror in the direction of the laser beam path from the half mirror; A scanning unit for reflecting the laser light so as to scan in the horizontal direction, a first surface, a second surface, and a third surface, the first surface receiving the laser light from the scanning system unit; A prism that reflects only the valley portion of the fingerprint of the finger placed on the second surface through the third surface, and a second that separates the laser light from the third surface of the prism into two. Half mirror and this second A plurality of laser light receiving means for transmitting laser lights of different wavelengths from each other with respect to the laser light separated by the half mirror, and detecting a thin line portion of the ridge of the fingerprint according to the intensity of the light received by the laser light receiving means A first step of converging a laser beam from the first laser beam projecting unit with the first lens, and a step of converging the laser beam from the first laser beam projecting unit with the second lens. A second step of converging the laser light from the laser light projecting means, and a third step of converging the laser light from the first and second lenses on the same optical axis by the first half mirror. And 4th moving the laser beam condensed by the first half mirror in the horizontal direction by the scanning system unit.
A fifth step of separating the reflected light from the prism into two, a sixth step of transmitting a first wavelength of one of the reflected lights separated by the half mirror, A seventh step of transmitting a second wavelength of the other reflected light separated by the mirror, an eighth step of converting the intensity of the reflected light from the laser light receiving unit into an electric signal, A ninth step of detecting a thinned portion of a fingerprint ridge from a ratio of electric signals, a tenth step of recording a position on the second surface of the prism when the thinned portion is detected, A first means for horizontally moving the laser light condensed by the first half mirror by the scanning system unit;
Step 1: moving the scanning system unit in the direction of the laser beam path when the horizontal scanning is completed by the scanning system unit;
A twelfth step returning to the step; and terminating all operations when the scanning in the laser beam path direction is completed by the scanning system unit, and entering the fourth step when the scanning in the laser beam path direction is not terminated. And a returning thirteenth step. 5. The fingerprint image thinning processing apparatus according to claim 4, wherein the scanning system unit includes a galvanometer mirror.