JPH0371280A - Image input device - Google Patents

Abstract

PURPOSE:To obtain a wide finger print image free from trapezoidal distortion by using a curved glass for a finger print impressing part. CONSTITUTION:When no finger is put on the curved glass body 1-1, input light to an image sensor 1-2 is fully reflected, so that the output signal level of the image sensor 1-2 goes higher than a binary slice level and all output signals from a comparator 5 are turned to '0'. When a finger is put on the body 1-1, a value smaller than the binary slice level is obtained on the projected line part of a finger print. Thereby, the setting of a finger can be detected by observing the output of the comparator 5. In this case, an elastic thin film is applied to the inside of the curved glass body 1-1 to improve adhesiveness with projected line. Consequently, the finger print image of the finger put on the body 1-1 can be detected along the curved face.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image input device, and more particularly to an image input device that optically detects a pattern to be verified, such as a fingerprint 2, and converts it into an electrical signal.

[Prior Art] Conventionally, as this type of image input device, the device shown in FIG. 2 is known. In FIG. 2, 20 is a prism, and one side of the prism 20 is illuminated by a light source 21. In FIG. The light from the light source 21 is totally reflected by the surface A-A' of the prism 20 and input to the detector 22 . As shown in FIG. 3, on the surface A-A' of the prism 20, where the fingerprint pattern of fingers 1-10 touches the prism 20, total reflection occurs due to sweat secreted from the skin and moisture on the pattern. Conditions collapse,
The light from the light source 21 causes diffuse reflection. on the other hand.

The total internal reflection condition does not collapse in areas where the fingerprint pattern does not touch. Therefore, the detector 22 can detect the difference in the amount of reflected light between the convex portions (hereinafter referred to as ridges) and concave portions of the fingerprint pattern as a grayscale fingerprint image.

The analog image signal output from the detector 22 is quantized by the A/D conversion circuit 23 and input to the storage circuit 24, where it is stored. The operator starts A/D conversion in the A/D conversion circuit 23 and writes data to the storage circuit 24 while watching the monitor 25.

This is executed by determining the image quality of the human-powered image and inputting an input start signal from the keyboard 26.

When an input start signal is input from the keyboard 26 to the control circuit, the control circuit 27 outputs a signal necessary for writing image data to the A/D conversion circuit 23 and the storage circuit 24, and the fingerprint image is stored in the storage circuit 24. be remembered. Further, the fingerprint image stored in the storage circuit 24 is stored in the interface 2.
8 to a host combinator (not shown). Such a device is disclosed in, for example, Japanese Patent Application Laid-Open No. 54-693.
00 and Japanese Unexamined Patent Publication No. 54-85600.

[Problems to be Solved by the Invention] Since the above-described conventional image-powered device uses a prism, the stamping surface on which the finger is placed is a flat surface.

Therefore, the input image is a flat imprint image, and there is a problem in that only a fingerprint image containing one trapezoidal distortion can be input.

Also, since the printing surface is glass, your fingers may be dry.

With rough fingers, there is a problem in that sufficient adhesion between the ridges and the glass surface cannot be obtained, and clear gradation images cannot be obtained.

Furthermore, when starting images manually, there was a problem in that the operator had to look at the monitor and give instructions from the keyboard.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image input device that can obtain clear images without distortion and that automatically starts manual input.

[Means for Solving the Problems] The image input device of the present invention includes a transparent body whose inner wall surface and outer wall surface form concentric cylindrical surfaces, and a transparent elastic thin film coated on the inner wall surface; A one-dimensional image sensor equipped with a fixed imaging system so as to be in focus and controlled to perform main scanning, an illumination means for illuminating an imaging area of the one-dimensional image sensor, and the one-dimensional image sensor the illumination means is fixed to the inner wall surface so as to satisfy a total reflection condition, and sub-scanning of the one-dimensional image sensor is performed along the outer wall surface while maintaining the total reflection condition. and a binarization unit that converts the output video signal of the one-dimensional image sensor into a binarized image signal based on a preset threshold.

a counting means for counting the frequency of "1" signal or "O" signal for each scan of the binarized image signal and outputting a counted value; The present invention is characterized in that it includes an output means that outputs a sub-scanning start signal when it detects that a sub-scanning start signal is detected.

[Example] Next, one embodiment of the present invention will be explained with reference to the drawings.

FIGS. 4 and 5 are configuration diagrams of the fingerprint detection section.

1-1 is a curved glass body whose inner wall surface is coated with an elastic thin film and whose inner and outer wall surfaces form concentric cylindrical surfaces, and the finger 1-10 is placed on the inner wall surface.

1-2 is a one-dimensionally arranged optical fiber lens 1-6
It is a one-dimensional image sensor equipped with

The optical fiber lens 1-6 is fixed so as to be focused on the inner wall surface of the curved glass body 1-1. 1-3 is an illumination unit that uniformly illuminates the imaging range of the image sensor 1-2. As shown in FIG. 5, the image sensor 1-2 and the illumination section 1-3 are fixed in a positional relationship that satisfies the total reflection condition on the inner wall surface of the curved glass body 1-1. This image sensor 1-2 detects and outputs an image on the inner wall surface of the curved glass body 1-1 using an optical fiber lens 1-6.

The principle of detection is the same as that using the prism described above.

The image sensor 1-2 and the illumination unit 1-3 are connected to the support stand 1-5.
is fixed on top. This support stand 1-5 is fixed to the rotating shaft of a pulse motor 1-4, and the rotating shaft of the pulse motor 1-4 is arranged on the virtual central axis of the curved glass 1-1. Therefore, when the pulse motor 1-4 rotates, the image sensor 1-2 and the illumination section 1-3 are connected to the curved glass body 1-
It moves along the outer wall surface of the curved glass body 1-1 while maintaining the total reflection condition on the inner wall surface of the curved glass body 1-1.

FIG. 1 shows a block diagram of the present invention.

The sub-scanning mechanism of the fingerprint detection unit 1, that is, the mechanical drive circuit is in a stopped state. On the other hand, the image sensor 1-2 is driven by a sensor drive circuit 2. That is.

Performs main scanning. After the image signal output from the image sensor 1-2 is input to the A/D conversion circuit 4.

Quantized. This quantized image signal is sent to the comparator circuit 5.
is input, and the binarized slice level is stored.

The output from the constant setting circuit 6 is compared for each pixel. The comparator circuit 5 outputs a signal '1' when the manually input signal for each pixel is smaller than a constant.

If it is larger, a signal "0" is output. A main scanning start signal is inputted to the counting circuit 7 from the sensor drive circuit 2, and the count value is cleared every - main scanning. In the counting circuit 7, the signal “
1", the total number of pixels smaller than the binarization slice level for each - main scan is calculated. When the finger is not placed on the curved glass body 1-1, Since all the input light to the image sensor 1-2 becomes totally reflected light, the output signal level of the image sensor 1-2 is only a value higher than the binarized slice level.

The output signals of the comparator circuit 5 are all "0°. On the other hand.

Lit your fingers! When placed, the convex part of the fingerprint pattern (hereinafter referred to as

(called ridges), values lower than the binarized slice level are obtained. The ratio largely depends on the adhesion between the ridge and the mounting surface. Therefore, by observing the output of the comparison circuit 5, placement of a finger can be detected. The counting circuit 7 detects the number of pixels in the portion where the ridge is in contact with the mounting surface on the lifetime scanning line. The output of this counting circuit 7 and the constant setting circuit 9
The output of the output signal is input to the comparator circuit 8 and compared. The comparison circuit 8 outputs a mechanical drive start signal when the output of the counting circuit 7 becomes larger than the value set in the constant setting circuit 9. When the mechanical drive start signal is input manually, the mechanical drive circuit 3 sends a drive pulse to the pulse motor 1-4 in the fingerprint detection unit 1 to execute sub-scanning of the fingerprint detection unit 1, that is, to start inputting an image.

The image signal thus captured is quantized by the A/D conversion circuit 4, and its output is input to the storage circuit 10 and stored. Furthermore, the image data stored in the storage circuit 10 is sent to a host computer (not shown) via an interface 11. In this way, by self-scanning of the one-dimensional image sensor, the fingerprint image of the finger placed on the curved glass body 1-1 can be detected along the curved surface.

Note that a known method is used to apply the transparent elastic thin film to the inner wall surface of the curved glass, and detailed description thereof will be omitted here.

Furthermore, although a curved glass body is used in the above embodiment, it is also possible to use a transparent curved plastic body.

[Effects of the Invention] As explained above, the present invention uses a curved glass for the fingerprint imprinting part, so the input image area is wider than when a prism is used, and a fingerprint image without trapezoidal distortion can be obtained.

Furthermore, by detecting changes in shading on the stamping surface, it is possible to detect the placement of a finger and automatically produce one image manually.

Furthermore, by coating the vitreous body wall with a transparent elastic thin film, high adhesion between the ridges and the stamping surface can be obtained.
Clear gradation images can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. Fig. 2 is a configuration diagram of a conventional fingerprint image human-powered device using a prism, Fig. 3 is a principle diagram of an image input method using the device shown in Fig. 2, and Fig. 4 is a perspective view of a fingerprint detection section of the present invention. , FIG. 5 is a partial cross-sectional view of the fingerprint detection section of FIG. 4. 1... Fingerprint detection unit, 2... Sensor drive circuit, 3...
・Mechanical drive circuit, 4.23...A/D conversion circuit, 5,
8... Comparison circuit, 6.9... Constant setting circuit, 7...
・Counting circuit, 10.24...Memory circuit, 11.28・
...Interface, 20...Prism, 21...
・Light source, 22...Detector, 25...Monitor, 26.
...Keyboard, 27...Control circuit, 1-1...Curved glass, 1-2...One-dimensional image sensor, 1-3
...Lighting section, 1-4...Pulse motor, 1-5...
・Support stand, 1-6...Optical fiber lens, 1-7・
...Transparent elastic thin film, 1-10...Finger.

Claims (1)

[Claims] 1. A transparent body whose inner wall surface and outer wall surface form concentric cylindrical surfaces, and which has a transparent elastic thin film on the inner wall surface, and an imaging system fixed so as to be focused on the inner wall surface, and which performs main scanning. a one-dimensional image sensor that is controlled to perform a one-dimensional image sensor, an illumination means that illuminates an imaging area of the one-dimensional image sensor, and a total reflection condition for the one-dimensional image sensor and the illumination means with respect to the inner wall surface. a drive means for sub-scanning the one-dimensional image sensor along the outer wall surface while maintaining the total reflection condition; Binarizing means for generating a binary image signal based on a threshold value, and counting means for counting the frequency of "1" or "0" for each scan of the binary image signal and outputting a counted value. , and output means for outputting a sub-scanning start signal when it is detected that the count value has exceeded a predetermined setting value.