JPH0816752A - Device and method for inputting fingerprint image - Google Patents

Abstract

PURPOSE:To obtain a clear and high-resolution fingerprint image by allowing laser light beams converged into an extremely small spot to two-dimensionally scan a prism and measuring reflected light intensity for each laser spot. CONSTITUTION:The laser light from a flood part 1 is made incident on a first galvanometer mirror 3 for allowing the laser light to scan in a main scanning direction through a first mirror 2 and converged into the extremely small spot by a first lens 4 to irradiate a prism 7. The laser light reflected from the prism 7 is inputted through a light receiving part 8 and an A/D converter 9 to a control part 10 as a digital electric signal. The control part 10 outputs a signal for driving the first galvanometer mirror 3 and a stepping motor 6 to allow the laser light to scan in a sub-scanning direction and forms the fingerprint image by converting the digital electric signal to image density data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fingerprint collation device for identifying an individual by using a fingerprint engraved on the surface of a finger of a human body, and more particularly, a fingerprint image input for inputting a fingerprint image of the finger surface into a computer or the like. The present invention relates to a device and an input method thereof.

[0002]

2. Description of the Related Art Most conventional fingerprint collation devices focus on the difference in reflectance due to the unevenness of the fingerprint and receive the reflected light from the finger to obtain the unevenness of the fingerprint as a grayscale image.

For example, referring to FIG. 9, a fingerprint image input device in a typical conventional fingerprint collation device satisfies the condition of total reflection at a contact surface between a light projecting portion 91 using white light as a light source and a finger. A prism 92 that reflects the white light that is incident from the light projecting unit 91 and an image pickup element 93 that receives the reflected light from the prism 92 to obtain a fingerprint image (see Japanese Patent Laid-Open No. 54-85600). .

That is, when the prism 92 is not touched by a finger, the white light incident from the light projecting portion 91 is totally reflected by the upper surface of the prism 92, and the image obtained by the image pickup element 93 becomes a bright image. . When a fingerprint is input, a finger is pressed against the upper surface of the prism 92. At this time,
Since the skin and the prism 92 are in contact with each other in the convex portion of the fingerprint, the condition of total reflection is not satisfied, and most of the white light from the light projecting portion 91 is absorbed by the skin and a part thereof is reflected by the contact surface. become. On the other hand, in the concave part of the fingerprint, the skin and the prism 9
Since 2 and 2 are not in contact with each other, the total reflection condition is satisfied, and the white light from the light projecting unit 91 is totally reflected on the contact surface,
It is incident on the image sensor 93. As a result, the concave portions of the fingerprint are bright and the convex portions are dark, so that a fingerprint image with contrast can be obtained.

[0005]

However, in the above-mentioned conventional fingerprint image input device, the finger on the prism is irradiated with the white light from the light projecting portion, and the reflected light is received by the image sensor to form the fingerprint image. At the time of obtaining, it is very difficult to make the intensity distribution of the white light which is the light source uniform, and there is a problem that the fingerprint image tends to become unclear due to the scattering of white light or chromatic aberration.

Further, the resolution of the fingerprint image depends on the resolution of the image sensor, and it is difficult to improve the resolution beyond the resolution of the image sensor.

The main object of the present invention is to solve the above-mentioned problems and to focus a laser beam in a very small spot shape when a fingerprint image is picked up. An object of the present invention is to provide a fingerprint image input device capable of obtaining a clear high-resolution fingerprint image by two-dimensionally scanning and measuring reflected light intensity for each laser spot to form an image.

[0008]

A fingerprint image input device of the present invention is a lens for focusing a laser beam having a predetermined constant wavelength into a spot having a predetermined size, and a laser spot focused by the lens. A mirror for scanning in the main scanning direction on the contact surface of the transparent polyhedron with the finger, and a stepping motor for scanning the laser spot focused by the lens in the sub-scanning direction on the contact surface with the finger of the transparent polyhedron, A light receiving unit that receives reflected light from the transparent polyhedron and converts the reflected light intensity into an electric signal, and image density data is generated by the electric signal from the light receiving unit, and a fingerprint image is formed from the image density data. , Scanning the laser spot relative to the mirror and the stepping motor by a predetermined number of steps in the main scanning direction and the sub scanning direction, respectively. That and a control unit for sending a drive control signal.

Another fingerprint image input device of the present invention is
A lens for focusing a laser beam having a predetermined constant wavelength into a spot having a predetermined size; and a laser spot focused by the lens for scanning the contact surface of the finger of the transparent polyhedron in the main scanning direction. No. 1 mirror, a stepping motor that scans the laser spot focused by the lens in the sub-scanning direction on the contact surface of the transparent polyhedron with the finger, and receives the reflected light from the transparent polyhedron and adjusts the reflected light intensity. A light receiving unit for converting into an electric signal and a second mirror which rotates in synchronization with the first mirror and reflects the reflected light from the transparent polyhedron so as to concentrate the reflected light on a predetermined position of the light receiving unit. Image density data is generated from the electric signal from the light receiving unit, a fingerprint image is formed from the image density data, and the first mirror and the stepping motor Then, a drive control signal for scanning the laser spot by a predetermined number of steps in the main scanning direction and the sub-scanning direction, respectively, is transmitted, and the reflected light from the transparent polyhedron is further transmitted to the second mirror by the light receiving unit. And a control unit that sends a drive control signal so as to concentrate on a predetermined position.

[0010]

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

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

Referring to FIG. 1, in the first embodiment, a light projecting section 1 for outputting a laser beam using a semiconductor laser or an LED as a light source, and a first projecting section for reflecting the laser beam output from the light projecting section 1 are provided. Mirror 2 and a first galvanometer mirror 3 that rotates in response to an analog electric signal and further reflects the laser light reflected by the first mirror 2.
And a first lens 4 which focuses the laser light reflected by the first galvanometer mirror 3 and narrows it down into a spot shape to adjust the optical path of the laser light, and a laser which is narrowed down into a spot shape through the first lens 4. A scanning system unit including a second mirror 5 that reflects light, a first mirror 2, a first galvanometer mirror 3, a first lens 4 and a second mirror 5 is provided in a main scanning direction according to an analog electric signal. A stepping motor 6 that moves the spot-shaped laser light reflected by the second mirror 5, and a prism 7 that reflects the spot-shaped laser light under the condition of total reflection on the contact surface with the finger. A light receiving unit 8 that detects the reflected light of the spot-shaped laser light from the prism 7 and outputs an analog electric signal corresponding to the optical intensity of the reflected light, and a light receiving unit 8 that outputs the analog electric signal. A / D converter 9 for converting an analog electric signal into a digital electric signal, and image density data is generated according to the digital electric signal converted by the A / D converter 9, and the image density is stored at a predetermined position in the internal memory 101. A controller 10 that stores data and outputs a digital control signal for controlling the operations of the first galvanometer mirror 3 and the stepping motor 6, and a fingerprint image based on the image density data stored by the controller 10. The display unit 11 for displaying and the first output from the control unit 10
A D / A converter 12 for converting a digital control signal for the galvanometer mirror 3 of FIG.
D / which converts a digital control signal for the stepping motor 6 output from the control unit 10 into an analog control signal
And an A converter 13.

FIG. 2 is a top view of a part of the first embodiment shown in FIG. 1 when viewed from above. FIG. 5 is an explanatory diagram showing the scanning order of laser spots on the contact surface of the prism 7 with the finger. FIG. 6 shows the display unit 1 corresponding to the position of the laser spot on the contact surface of the prism 7 with the finger.
It is explanatory drawing showing the state of each 1 pixel.

Next, the operation of the first embodiment of the present invention will be described with reference to FIGS. 1, 2, 5 and 6.

The laser light output from the light projecting unit 1 is the first
After being reflected by the mirror 2, it is incident on the first galvanometer mirror 3. This first galvanometer mirror 3
Is a digital control signal output from the control unit 10
The laser beam is scanned in the main scanning direction according to the analog control signal converted by the A converter 13. The laser light reflected by the first galvanometer mirror 3 is focused into a spot-shaped laser light by the first lens 4, and the optical path is adjusted so that the laser light is reflected on the contact surface of the isosceles prism 7 which is a transparent polyhedron with a finger. Is irradiated. At this time, on the contact surface between the prism 7 and the finger, the spot contacting the convex portion of the fingerprint does not satisfy the condition of total reflection, so that the spot-shaped laser light is diffusely reflected. On the other hand, on the contact surface between the prism 7 and the finger, the spot contacting the concave portion of the fingerprint satisfies the total reflection condition, so that the spot-shaped laser light is totally reflected.

As described above, in the present invention, by using the laser light as the light source, it is possible to eliminate the scattering of white light or the chromatic aberration, which has been a problem in the past, thereby preventing the fingerprint image from becoming unclear. It becomes possible.

Further, since the laser light is focused in a spot shape and the contact surface of the prism with the finger is two-dimensionally scanned and irradiated, it is possible to eliminate the uneven light quantity on the contact surface and to make the intensity distribution uniform. Becomes

The intensity of the spot-shaped laser light reflected by the prism 7 is detected by the light receiving portion 8 and converted into an analog electric signal. Subsequently, the control unit 10 receives the digital electric signal converted by the A / D converter 9, and writes it in the internal memory 101 as image density data at an address corresponding to the position irradiated by the prism 7. Then, when it is determined that one line has been scanned in the main scanning direction, the control unit 10 is an optical system unit including the first mirror 2, the first galvanometer mirror 3, the first lens 4 and the second lens 5. A digital control signal is output to the stepping motor 6 for driving the first galvanometer mirror 3 in the sub-scanning direction to move one line in the sub-scanning direction. To 1
A digital control signal is output to scan one line.
By repeating such processing until the end of the sub-scanning direction, two-dimensional scanning of the fingerprint by the spot-shaped laser light is realized. The reflected light intensity of the laser light stored in the internal memory 101 is displayed on the display unit 11 as an image showing the intensity distribution. 5 and 6, the pixel 19 is a point where the reflected light intensity at the position of the laser spot 18 irradiated with the laser light is recorded as image density data by the control unit 11 and displayed on the display unit 11. That is, since the size of the laser spot becomes a factor that determines the resolution of the fingerprint image on the display unit 11, the size of the laser spot by the first lens 4 and the scanning width by the first galvanometer mirror 3 and the stepping motor 6 can be obtained. The resolution can be improved up to about the wavelength of the maximum laser light by making it smaller.

Further, the control unit 1 which is a feature of the first embodiment.
The operation of 0 will be described with reference to FIG.

First, the control unit 11 sends a digital control signal for moving the first galvanometer mirror 3 to the initial position to the first galvanometer mirror 3, and the laser spot is initially set on the contact surface of the prism 7 with the finger. It is moved to the position (FIG. 7, step S71). Next, the control unit 10
Receives a digital electric signal corresponding to the intensity of reflected light from the prism 7 detected by the light receiving unit 8 and writes the digital electric signal in a predetermined position of the internal memory 101 as image density data (FIG. 7, step S72). Further, the control unit 10 sends a digital control signal for moving the first galvanometer mirror 3 in the main scanning direction by one step to the first galvanometer mirror 3, and the laser spot is scanned on the contact surface of the prism 7 with the finger. 1 step in the direction (Fig. 7, step S
73). Here, the control unit 10 determines whether or not the scanning of the laser light in the main scanning direction is completed (FIG. 7, step S74), and if not completed, the process returns to step S72 and the reflected light from the light receiving unit 8 continues. The intensity signal is received and recorded in the internal memory 101 as image density data, and when it is finished, a digital control signal for moving the stepping motor 6 in the sub-scanning direction by one step is sent to the stepping motor, and the laser beam is sub-scanned. It is moved one step in the direction (FIG. 7, step S75). Then, the control unit 10
Determines whether or not the scanning of the laser beam in the sub-scanning direction is completed (FIG. 7, step S76), and if not completed, the process returns to step S71 to move the laser spot to the initial position again for scanning. If finished, all control operations are finished.

Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a block diagram showing a second embodiment of the present invention. FIG. 4 is a top view of a part of the second embodiment shown in FIG. 3 when viewed from above.

Referring to FIG. 3, in the second embodiment, a light projecting section 1 for outputting a laser beam using a semiconductor laser, an LED or the like as a light source, and a first projecting section for reflecting the laser beam outputted from the light projecting section 1 are provided. Mirror 2, a first galvanometer mirror 3 that rotates in response to an input analog electric signal, and further reflects the laser light reflected by the first mirror 2, and a first galvanometer mirror 3 that reflects the laser light. A first lens 4 that focuses the laser light and narrows it down into a spot shape to adjust the optical path of the laser light; a second mirror 5 that reflects the laser light that is narrowed down into a spot shape by the first lens 4; The scanning system unit composed of the first mirror 2, the first galvanometer mirror 3, the first lens 4 and the second mirror 5 is moved in the main scanning direction according to the analog electric signal. The spot-shaped laser light reflected by the ring motor 6 and the second mirror 5 is incident, and the spot-shaped laser light is reflected by the prism 7 under the condition of total reflection on the contact surface with the finger. The third mirror 14 that reflects the reflected laser light again, the second lens 15 that refocuses the laser light reflected by the third mirror 14, and the second lens 15 that rotates according to the input analog electric signal, The second galvanometer mirror 16 that reflects the laser light focused by the second lens 15 again, and the reflected light intensity of the laser light reflected by the second galvanometer mirror 16 are detected, and the analog according to the reflected light intensity is detected. Light receiving unit 8 that outputs an electric signal, A / D converter 9 that converts the analog electric signal output from light receiving unit 8 into a digital electric signal, and A / D converter 9 Image density data is generated according to the converted digital electric signal, the image density data is stored in a predetermined position of the internal memory 101, and the first galvanometer mirror 3, the second galvanometer mirror 16 and the stepping motor 6 are operated. Control unit 10 that outputs a digital control signal for controlling the operation
A display unit 11 for displaying a fingerprint image based on the image density data stored in the control unit 10; and a digital control signal for converting the digital control signal output from the control unit 10 to the first galvanometer mirror 3 into an analog control signal. / A converter 12, a D / A converter 13 for converting a digital control signal for the stepping motor 6 output from the control unit 10 into an analog control signal, and digital control for the second galvanometer mirror 16 output from the control unit 10. D / A converter 1 for converting signals to analog signals
7 and 7.

Next, the operation of the second embodiment will be described with reference to FIGS. 3 and 4.

The laser light output from the light projecting section 1 is the first
After being reflected by the mirror 2, it is incident on the first galvanometer mirror 3. This first galvanometer mirror 3
Is a digital control signal output from the control unit 10
The laser beam is scanned in the main scanning direction according to the analog control signal converted by the A converter 13. The laser light reflected by the first galvanometer mirror 3 is focused into a spot-shaped laser light by the first lens 4, and the optical path is adjusted so that the laser light is reflected on the contact surface of the isosceles prism 7 which is a transparent polyhedron with a finger. Is irradiated. At this time, on the contact surface between the prism 7 and the finger, the spot contacting the convex portion of the fingerprint does not satisfy the condition of total reflection, so that the spot-shaped laser light is diffusely reflected. On the other hand, on the contact surface between the prism 7 and the finger, the spot contacting the concave portion of the fingerprint satisfies the total reflection condition, so that the spot-shaped laser light is totally reflected. The laser light reflected by the prism 7 is reflected again by the third mirror 14 and is incident on the second lens 15. The second lens 15 focuses the incident laser light and supplies it to the second galvanometer mirror 16. The second galvanometer mirror 16 is synchronized with the first galvanometer mirror 3 installed on the incident side of the prism 7 in accordance with the analog control signal obtained by converting the digital control signal from the control unit 10 by the D / A converter 17 for one step. Each of them is driven so as to rotate in the main scanning direction, and the reflected light is controlled to be detected at one point of the light receiving portion 8.

That is, the third mirror 14, the second lens 15, and the second galvanometer mirror 16 are used to constantly concentrate the reflected light from the prism 7 on the light receiving portion 8 to thereby form a light receiving portion. It is possible to reduce the influence of uneven sensitivity due to the incident position of the laser light on the image pickup device 8 (image pickup device) 8 and to reduce the size of the light receiving unit 8 (image pickup device) itself.

The spot-shaped laser light reflected by the prism 7 is detected by the light receiving portion 8 and converted into an analog electric signal. Subsequently, the control unit 10 receives the digital electric signal converted by the A / D converter 9, and writes it in the internal memory 101 as image density data at an address corresponding to the position irradiated by the prism 7. And 1 in the main scanning direction
If it is determined that one line has been scanned, the control unit 10 determines the first mirror 2, the first galvanometer mirror 3, the first lens 4, the second lens 5, the third mirror 14, and the second lens 15. , A digital control signal is output so as to move one line in the sub-scanning direction to the stepping motor 6 for driving the optical system unit including the second galvanometer mirror 16 and the light receiving unit 8 in the sub-scanning direction. A digital control signal is output to the first galvanometer mirror 3 and the second galvanometer mirror 16 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-shaped laser light is realized.

The control unit 1 which is a feature of the second embodiment.
The operation of 0 will be described with reference to FIG.

First, the control unit 11 sends a digital control signal for moving the first galvanometer mirror 3 and the second galvanometer mirror 16 to the initial position to the first galvanometer mirror 3 and the second galvanometer mirror 16, respectively. The laser spot is sent to move the laser spot to the initial position of the contact surface of the prism 7 with the finger, and the reflected light of the prism 7 is made incident on one point of the light receiving portion 8 (FIG. 8, step S81). Then, the control unit 10 controls the light receiving unit 8
A digital electric signal corresponding to the intensity of the reflected light from the prism 7 detected in step S8 is received and written as image density data at a predetermined position in the internal memory 101 (FIG. 8, step S8).
2). Further, the control unit 10 sends a digital control signal for moving the first galvanometer mirror 3 in the main scanning direction by one step to the first galvanometer mirror 3 (FIG. 8, step S83) and further synchronizes with this digital control signal. Then, a digital control signal for moving the second galvanometer mirror 16 in the main scanning direction by one step is sent to the second galvanometer mirror 16 (FIG. 8, step S8).
4). As a result, the laser spot can be moved one step in the main scanning direction on the contact surface of the prism 7 with the finger, and the reflected light of the prism 7 can be concentrated on one point of the light receiving portion 8. Here, the control unit 10 determines whether or not the scanning of the laser light in the main scanning direction is completed (FIG. 8, step S).
85), if not completed, the process returns to step S82 to continuously receive the digital electric signal corresponding to the reflected light intensity signal from the light receiving unit 8 and use it as the image density data in the internal memory 1
No. 01 is recorded, and when it is completed, a digital control signal for moving the stepping motor 6 in the sub-scanning direction by one step is sent to the stepping motor 6, and the laser beam is moved by one step in the sub-scanning direction (FIG. 8, step). S8
6). Then, the control unit 10 determines whether or not the scanning of the laser light in the sub-scanning direction is completed (FIG. 8, step S87), and if not completed, returns to step S81 to move the laser spot to the initial position again. Then, scanning is performed, and if the scanning is completed, all control operations are completed.

[0030]

As described above, in the present invention, the laser light is focused into a very small spot shape, and the laser spot is two-dimensionally scanned on the contact surface of the prism with the finger. By recording the image density data according to the reflected light intensity, it is possible to make the irradiation intensity distribution of the light source uniform, and as a result, it is possible to obtain a clear fingerprint image without adverse effects due to light scattering and chromatic aberration. . Further, in the present invention, the resolution of the fingerprint image can be improved to about the wavelength of the laser beam by adjusting the size of the laser spot and the scanning step width to be small, thereby obtaining a clear fingerprint image. It is possible.

Further, an optical system unit on the side for collecting the reflected light from the prism on the light receiving portion in synchronization with the optical system unit (including the first galvanometer mirror) on the side where laser light is incident on the prism and scans. Since the (including the second galvanometer mirror) is driven, the reflected light can always be detected at one point in the light receiving section, and as a result, uneven sensitivity of the light receiving section (imaging element) due to the incident position of the reflected light from the prism can be eliminated, and The light receiving unit (imaging device) itself can be downsized.

[0032]

[Brief description of drawings]

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

[0033]

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

[0034]

FIG. 3 is a configuration diagram showing a second exemplary embodiment of the present invention.

[0035]

FIG. 4 is a top view of a part of the second embodiment in FIG. 3 when viewed from above.

[0036]

FIG. 5 is an explanatory diagram showing a scanning order of laser spots.

[0037]

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

[0038]

FIG. 7 is a flowchart showing an operation of the control unit 10 in FIG.

[0039]

FIG. 8 is a flowchart showing an operation of the control unit 10 in FIG.

[0040]

FIG. 9 is an explanatory diagram showing a configuration of a conventional fingerprint image input device.

[0041]

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Projection part 2 1st mirror 3 1st galvanometer mirror 4 1st lens 5 2nd mirror 6 Stepping motor 7 Prism 8 Light receiving part 9 A / D converter 10 Control part 11 Display part 12 D / A converter 13 D / A converter 14 Third mirror 15 Second lens 16 Second galvanometer mirror 17 D / A converter 18 Laser spot 19 Pixel 101 Internal memory

Claims (8)

[Claims] 1. A lens for focusing laser light having a predetermined constant wavelength into a spot having a predetermined size, and a laser spot focused by the lens is main-scanned on a contact surface of a transparent polyhedron with a finger. A mirror that scans in the direction, a stepping motor that scans the laser spot focused by the lens in the sub-scanning direction on the contact surface of the transparent polyhedron with the finger, and receives the reflected light from the transparent polyhedron and reflects the reflected light. A light receiving section for converting the intensity into an electric signal, and image density data is generated by the electric signal from the light receiving section, and a fingerprint image is formed from the image density data, and the laser spot is applied to the mirror and the stepping motor. And a control unit for transmitting a drive control signal for scanning each of the main scanning direction and the sub scanning direction by a predetermined number of steps. Fingerprint image input apparatus characterized by. 2. A first step of focusing a laser beam having a predetermined constant wavelength into a spot having a predetermined size, and rotating a mirror of the laser spot focused by the lens to form a transparent polyhedron. A second step of moving to a predetermined initial position in the main scanning direction on the contact surface with the finger, and converting the intensity of the reflected light received from the transparent polyhedron into an electric signal, and image density data is obtained from the electric signal. A third step of generating and recording, a fourth step of moving the laser spot in the main scanning direction by a predetermined width by rotating the mirror, and ending the scanning of the laser spot in the main scanning direction. Then, the laser spot is moved in the sub-scanning direction by a predetermined width by the stepping motor to finish the scanning in the main scanning direction. If not, a fifth step of returning to the third step, and when scanning in the sub-scanning direction by the laser spot is completed, all operations are completed, and when scanning in the sub-scanning direction is not completed, the second step is completed. And a sixth step of returning to the step of. 3. A lens for focusing laser light having a predetermined constant wavelength into a spot having a predetermined size, and a laser spot focused by the lens is subjected to main scanning on a contact surface of a transparent polyhedron with a finger. A first mirror for scanning in a direction, a stepping motor for scanning a laser spot focused by the lens in a sub-scanning direction on a contact surface of the transparent polyhedron with a finger, and receiving reflected light from the transparent polyhedron. , A light receiving unit for converting the intensity of the reflected light into an electric signal, and rotating in synchronization with the first mirror to reflect the reflected light from the transparent polyhedron so as to concentrate the reflected light from the transparent polyhedron at a predetermined position of the light receiving unit. Image density data is generated by an electric signal from the second mirror and the light receiving unit, and a fingerprint image is formed from the image density data. A drive control signal for scanning the laser spot by a predetermined number of steps in the main scanning direction and the sub-scanning direction is sent to the ping motor, and the reflected light from the transparent polyhedron is further transmitted to the second mirror. A fingerprint image input device, comprising: a control unit that sends a drive control signal so as to concentrate the light receiving unit on a predetermined position. 4. A first step of focusing laser light having a predetermined constant wavelength into a spot having a predetermined size, and rotating a first mirror to rotate the laser spot focused by the lens. The light reflected from the transparent polyhedron is moved by moving it to a predetermined initial position in the main scanning direction on the contact surface of the transparent polyhedron with the finger and rotating the second mirror in synchronization with the first mirror. A second step of reflecting the light at a predetermined initial position of the light receiving section, and converting the reflected light intensity detected by the light receiving section into an electric signal,
A third step of generating and recording image density data from the electric signal, and a fourth step of rotating the first mirror to move the laser spot in the main scanning direction by a predetermined width, A fifth step of concentrating the reflected light from the transparent polyhedron at the initial position of the light receiving section by rotating the second mirror in synchronization with the first mirror; and a main scanning direction by the laser spot. A sixth step of moving the laser spot in the sub-scanning direction by a predetermined width by the stepping motor when the scanning of the above is finished, and returning to the third step when the scanning of the main scanning direction is not finished; When the scanning in the sub-scanning direction by the laser spot is completed, all the operations are completed, and the scanning in the sub-scanning direction is not completed. And a seventh step of returning to the second step, the fingerprint image input method. 5. The fingerprint image input device according to claim 1, wherein the mirror is a galvanometer mirror. 6. The fingerprint image input method according to claim 2, wherein the mirror is a galvanometer mirror. 7. The fingerprint image input device according to claim 3, wherein both the first mirror and the second mirror are galvanometer mirrors. 8. The fingerprint image input method according to claim 4, wherein both the first mirror and the second mirror are galvanometer mirrors.