JPH0827833B2 - Fingerprint image input device - Google Patents

Description

The present invention relates to a fingerprint image input device, and more particularly to an input device for directly inputting a fingerprint image from a finger without using ink.

[Conventional technology]

Conventionally, the device shown in FIG. 2 is known as an input device of this type. Referring to FIG. 2, reference numeral 20 is a right-angle prism, and one surface of the prism 20 is illuminated by a lamp 21.
The light from the lamp 21 is totally reflected by the surface AA ′ of the right-angle prism 20 and input to the TV camera 22. As shown in FIG. 3, in the area where the skin of the finger FNG is in contact with the prism 20 on the surface AA ′ of the right-angled prism 20, the total reflection condition is broken due to slight sweat secreted from the skin, and diffuse reflection occurs, The part that is not touched is totally reflected. Therefore, the TV camera 22 can detect the difference in the amount of reflected light between the peak portion and the valley portion of the fingerprint as a fingerprint image.

The fingerprint image signal (analog signal) output from the TV camera 22 is quantized by the A / D conversion circuit 23, input to the storage circuit 24, and stored. The operator starts the A / D conversion in the A / D conversion circuit 2 and writes to the memory circuit 24 by the monitor 25.
The user judges the image quality while looking at it and gives an instruction to start input from the keyboard 26. When there is an instruction to start input from the keyboard 26,
The control circuit 27 outputs a signal necessary for the operation of writing the image data to the A / D conversion clock and the storage circuit 24, and the fingerprint image data is stored in the storage circuit 24. In addition, the memory circuit 24
The fingerprint image data stored in the computer is input to a host computer (not shown) via the interface 28.

[Problems to be solved by the invention]

By the way, since the conventional input device uses the rectangular prism, the surface on which the finger as the input object is placed is a flat surface. Therefore, there is a problem that only a small part of the fingerprint image of the finger can be input because the proportion of the finger touching the prism surface is small. Furthermore, since the image is taken with a TV camera from an oblique direction, there is the problem that the detected fingerprint image can be obtained with trapezoidal distortion. Moreover, there is a problem that the operator has to look at the monitor and give an instruction from the keyboard to start inputting the image.

[Means for solving problems]

The fingerprint image input device according to the present invention comprises a transparent body whose inner and outer wall surfaces are curved so as to form concentric cylindrical surfaces, and an imaging system which is fixed to the inner wall surface of the transparent body so as to be in focus. A one-dimensional image sensor that is controlled so as to repeat main scanning, an illuminating unit that uniformly illuminates the linear imaging area of the one-dimensional image sensor, and an inner surface of a transparent body that illuminates the one-dimensional image sensor and the illuminating unit. A driving means which is fixed so as to satisfy the total reflection condition, and which maintains the total reflection condition and performs sub-scanning of the one-dimensional image sensor along the outer circumference of the transparent body; and an output video of the one-dimensional image sensor. Binarizing means for binarizing a signal with a preset threshold value, and counting means for counting the frequency of the "1" signal or "0" signal for each main scan of the binarized image signal When,
When it is detected that the frequency of the counted "1" signal or "0" signal is equal to or more than a predetermined set value, the sub-scanning start signal is output.

〔Example〕

 Next, the present invention will be described with reference to examples.

First, the configuration of the fingerprint detection unit will be described with reference to FIGS. 4 and 5. 1-1 is a transparent glass body that is curved so that the inner wall surface and outer wall surface become concentric cylindrical surfaces.
It will be a platform for directly mounting. Reference numeral 1-2 is a one-dimensional image sensor including one-dimensionally arranged optical fiber lenses 1-6. The optical fiber lens 1-6 is the curved glass body 1
It is fixed to the inner wall surface of -1 so that it is in focus. 1
An illuminator -3 uniformly illuminates the imaging range of the image sensor 1-2. As shown in FIG. 5, the image sensor 1-2 and the illuminator 1-3 are fixed on the inner wall surface of the curved glass body 1-1 in such a positional relationship that the total reflection condition is satisfied. The optical fiber lens 1-6 of the image sensor 1-2 detects and outputs an image on the inner wall surface of the curved glass body 1-1. The principle of detection is the same as in the case of using the above-mentioned prism, and the difference in the intensity of light reflected from the touched part and the non-touched part of the skin is detected by the image sensor 1.
-2 is converted into an electric signal and detected.

The image sensor 1-2 and the illuminator 1-3 have a support base 1-
It is fixed on top of 5. This support 1-5 is fixed to the rotation shaft of the pulse motor 1-4, and the rotation shaft of the pulse motor 1-4 is arranged on the central axis of the curved glass body 1-1. Therefore, when the pulse motor 1-4 rotates, the image sensor 1-2 and the illuminator 1-3 are curved glass bodies 1-
While keeping the condition of total reflection with respect to the inner wall surface of No. 1, the inner wall surface of No. 1 moves along the outer wall surface of the curved glass body 1-1.

Referring also to FIG. 1, when the fingerprint input is started, the fingerprint detection unit 1
The sub-scanning mechanism, that is, the pulse motor 1-4 is in a stopped state. On the other hand, the image sensor 1-2 is driven by the sensor drive circuit 2. That is, the main scanning is performed. The image signal output from the image sensor 1-2 is input to the A / D conversion circuit 4 and quantized. The quantized image signal is input to the comparison circuit 5 and compared with the output from the constant setting circuit 6 in which the binarized slice level is stored, for each pixel. The comparator circuit 5 outputs a signal "1" when the input signal is smaller than a constant, and outputs a signal "0" when the input signal is large for each pixel. The main scanning start signal is input to the counting circuit 7 from the sensor driving circuit 2, and the count value is cleared for each main scanning. Since the counting circuit 7 counts the number of signals "1", the total number of pixels smaller than the binarized sly level is calculated for each main scanning. When no finger is placed on the curved glass body 1-1, all the input light to the image sensor 1-2 becomes a total reflection component, so the image sensor 1-2
The output signal level of is only higher than the binarized slice level, and the output signals of the comparison circuit 5 are all "0".
On the other hand, when a finger is placed, a value lower than the binarized slice level is obtained in the mountain portion of the fingerprint, and the ratio increases as the sweat increases. Therefore, by observing the output of the comparison circuit 5, it is possible to know whether or not the finger is placed.
The counting circuit 7 finds the number of pixels, that is, the area of the mountain portion of the fingerprint on one main scan. The output of the counting circuit 7 and the output of the constant setting circuit 9 are input to the comparison circuit 8 and compared. When the output of the counting circuit 7 becomes larger than the value set in the constant setting circuit 9, that is, when the peak portion of the fingerprint exceeds the area set in the constant setting circuit 9, Outputs a mechanical drive start signal. When the mechanical drive start signal is input, the mechanical drive circuit 3 sends a drive pulse to the pulse motor 1-4 in the fingerprint detection unit 1 to cause the fingerprint detection unit 1 to perform sub scanning. The image signal picked up and output by this operation is quantized by the A / D conversion circuit 4, and its output is input to and accumulated in the storage circuit 10. Further, the image data stored in the storage circuit 10 is sent to a host computer (not shown) via the interface 11. As described above, the main scanning is performed by the one-dimensional image sensor self-scanning, and the sub-scanning is performed mechanically, that is, by the pulse motor 1-4, so that the fingerprint of the finger pressed on the curved glass body 1-1. The image can be detected along the curved surface. Although a curved glass body is used in the above embodiment, a transparent curved plastic body may be used.

〔The invention's effect〕

As described above, according to the present invention, since the fingerprint image of the finger pressed on the curved surface of the curved glass body is detected, there is an effect that the detection area is wide and the fingerprint image without graphic distortion can be detected. . Further, there is an effect that it is possible to automatically detect that a finger is placed and input an image. That is, the image can be input without the intervention of the operator.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram of a fingerprint image input device using a conventional prism, FIG. 3 is a diagram showing the principle of detection by total reflection, and FIG. FIG. 5 is a diagram showing the fingerprint detecting unit of the present invention in detail, and FIG. 5 is a diagram showing the positional relationship between the one-dimensional image sensor, the optical fiber, and the illuminator and the curved glass body. 1 is a fingerprint detection unit, 2 is a sensor drive circuit, 3 is a mechanical drive circuit, 4
Is an A / D conversion circuit, 5 and 8 are comparison circuits, 6 and 9 are constant setting circuits, 7 is a counting circuit, 10 is a memory circuit, 11 is an interface, 1
-1 is curved glass, 1-2 is one-dimensional image sensor, 1-3
Is an illuminator, 1-4 is a pulse motor, 1-5 is a support for the image sensor and the illuminator, and FNG is a finger.

Claims (1)

[Claims] 1. A main body is provided with a transparent body whose inner and outer wall surfaces are curved so as to form concentric cylindrical surfaces, and an imaging system which is fixed to the inner wall surface of the transparent body so as to be in focus. Controllable one-dimensional image sensor, illuminating means for referencing the imaging area of the one-dimensional image sensor, total reflection conditions for the one-dimensional image sensor and the illuminating means with respect to the inner wall surface of the transparent body. And a driving means for performing sub-scanning of the one-dimensional image sensor along the outer wall surface of the transparent body while maintaining the total reflection condition, and presetting an output video signal of the one-dimensional image sensor. Binarizing means for binarizing the binarized threshold value, counting means for counting the frequency of "1" signal or "0" signal for each main scanning of the binarized image signal, and this counting The frequency of the generated "1" signal or "0" signal is more than the set value. When it is detected that the since the fingerprint image input apparatus characterized by an output means for outputting the sub-scanning start signal.