JPH0371279A - Image input device - Google Patents

Abstract

PURPOSE:To obtain a wide finger print image free from trapezoidal distortion by using a transparent body forming concentrical cylinder faces by its inwall face and external wall face for a finger print impressing part. CONSTITUTION:When no finger is put on the inwall face of a glass body 1-1, input light to the glass body 1-1 is totally reflected on the inwall face, so that the output signal level of an image sensor 1-2 goes higher than a binary slice level and all output signals of a comparator 6 are turned to '0'. When a finger is put on the inwall face, irregular reflection is generated on projected line parts and a value smaller than the binary slice level is obtained. Namely, '1' is outputted from the comparator 6. Thereby, the setting of a finger can be detected by observing the output of the comparator 6. Since an elastic thin film is applied to the glass body 1-1, adhesiveness to the projected line is increased and a clear image can be obtained, so that the detecting accuracy can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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 9, 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.

20 is a prism, and the prism 20 is illuminated by a light source 21. The light from the light source 21 is directed to the surface A of the prism 20.
It is totally reflected at -A' and input to the detector 22. As shown in FIG.
In the area where the -10 fingerprint pattern touches the prism 20, the conditions for total reflection are disrupted due to sweat secreted from the skin and moisture on the pattern, causing diffuse reflection of the light from the light source 21. on the other hand.

The total internal reflection condition does not collapse in areas where the skin pattern does not touch. Therefore, the detector 22 is located at the convex portion of the pattern (hereinafter referred to as “convex portion”).

The difference in the amount of reflected light between the ridges (called ridges) and the recesses can be detected as a grayscale fingerprint image.

The analog image signal output from the detector 22 is quantized by the A/D conversion circuit 23, and then manually transferred to the storage circuit 24.
be remembered. The operator starts A/D conversion in the A/D conversion circuit 23 and writes data to the memory circuit 24 using the monitor 2.
5, judge the image quality of the input image, and press keyboard 2.
This is executed by inputting an input start signal from 6. When an input start signal is input from the keyboard 26, the control circuit 27 sends signals to the A/D conversion circuit 23 and the memory circuit 24.
The signals necessary for writing image data to the
The fingerprint image is stored in the storage circuit 24. Further, the fingerprint image stored in the storage circuit 24 is input to a host computer (not shown) via an interface 28.

A device like this.

For example, JP-A-54-69800 and JP-A-54-
It is disclosed in Japanese Patent No. 85600.

[Problems to be Solved by the Invention] Since the conventional image input device described above uses a prism, the printing surface on which the finger 1-10 is placed is a flat surface. Therefore, the input image is a flat stamped image.

There was a problem in that only fingerprint images containing trapezoidal distortion could 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 is a problem in that the operator must look at the monitor 25 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 and distortion-free images and that automatically starts inputting the images.

[Means for Solving the Problems] An 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, and the inner wall surface. a one-dimensional image sensor equipped with a fixed imaging system and controlled to perform main scanning so as to focus on the one-dimensional image sensor; The image sensor and the illumination means are fixed to the inner wall surface so as to satisfy a total reflection condition, and the one-dimensional image sensor is fixed along the outer wall surface while maintaining the total reflection condition. sub-scanning means for performing sub-scanning; binarization means for binarizing the output video signal of the one-dimensional image sensor using a preset threshold; “1° signal or “0” of the binarized image signal
``a counting means for counting the frequency of the signal;
output means for outputting a main scanning start signal when it is detected that the frequency of the 11 signal or the '0'' signal has exceeded a predetermined setting value; and a control means for controlling to repeat sub-scanning every predetermined number of main scans, and for controlling to sub-scan the entire surface of the imaging area when receiving the main-scanning start signal. It is a feature.

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

First, the configuration of the fingerprint detection section will be explained with reference to FIGS. 4 and 5. 1-1 is a glass body whose inner wall surface is coated with a transparent elastic thin film so that the inner wall surface and the outer wall surface are the same cylindrical surface, on which the finger 1-10 is placed. Since a known method for applying the elastic body can be used, detailed description thereof will be omitted here. 1-2 is a one-dimensional image sensor including optical fiber lenses 1-6 arranged one-dimensionally. The optical fiber lens 1-6 is connected to the glass body 1-1.
It is fixed so that the focus is on the inner wall of the 1-3 is an illumination unit that uniformly illuminates the imaging range of the image sensor 1-2. As shown in FIG. 5, image sensor 1-2
and the illumination section 1-3 are fixed in a positional relationship that satisfies the total internal reflection condition on the inner wall surface of the glass body 1-1. This image sensor 1-2 detects and outputs an image on the inner wall surface of the glass body 1-1 using an optical fiber lens 1-6. The detection principle is the same as the conventional one.

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 to coincide with the virtual central axis of the glass body 1-1.

Therefore, when the pulse motor 1-4 rotates, the image sensor 1-2 and the illumination unit 1-3 are exposed to the inner wall surface of the glass body 1-1 while maintaining the total reflection condition. Move along the outer wall surface.

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

The image sensor 1 - 2 of the fingerprint detection section 1 is driven by a sensor drive circuit 2 . This is called main scanning. Further, the sensor drive circuit 2 outputs a main scanning start signal to the preliminary scanning control circuit 3. The preliminary scan control circuit 3 receives the main scan start signal and outputs a preliminary sub-scan start signal every 64 main scans, for example, when the number of main scans 9 is smaller than the number of main scans required to scan the entire scanning area. Occur. When this preliminary sub-scanning start signal is input, the mechanical drive circuit 4 repeats sub-scanning every 64 main scans. That is, as shown in FIG. 6, sub-scanning is repeated for 64 main scans (area C-C), which is a part of the entire scan area BB' (for example, 512 main scans). This is because if the main scan is only one line, if one line of scanning happens to hit the trough of the fingerprint, the placement of the finger cannot be detected. The main scanning and sub-scanning are performed to detect whether a finger is placed on the glass body 1-1 of the fingerprint detection section 1.

The image signal output from the fingerprint detection section 1 is manually input to the A/D conversion circuit 5 and quantized. This quantized image signal is input to a comparator circuit 6, where a binarized slice level is stored. The output from the constant setting circuit 7 is compared for each pixel. The comparator circuit 6 outputs a signal "1" if the input image signal is smaller than a constant, and outputs "0°" if it is larger than a constant to the counting circuit 8 for each pixel.Then, the counting circuit 8 counts the signal "1". I do. Counting is performed until the preliminary scanning start signal is inputted to the counting circuit 8 from the preliminary scanning control circuit 3, and the counted value is outputted to the comparator circuit 9 every 64 main scannings, and then cleared. That is, the counting circuit 8 calculates the number of pixels smaller than the binarization slice level every 64 main scans.

When a finger is not placed on the inner wall surface of the glass body 1-1, all of the light input to the glass body 1-1 is totally reflected on the inner wall surface, so the output signal level of the image sensor 1-2 is Only values higher than the digitized slice level are obtained, and all output signals of the comparator circuit 6 become "0". On the other hand, when a finger is placed, a value lower than the binarized slice level is obtained because diffuse reflection occurs at the ridge portion. In other words, “1” is output from the comparator circuit 6.
is output. Therefore, by observing the output of the comparison circuit 6, it is possible to detect placement of a finger. Here, since the glass body 1-1 is coated with the elastic thin film 1-7, the adhesiveness with the ridges is high and the image becomes clear, thereby improving detection accuracy.

Every 64 main scans, the counting circuit 8 receives the “
1'' is output, and a predetermined value is output from the constant setting circuit 10 and input to the comparison circuit 9.

The comparison circuit 9 compares the output value from the counting circuit 8 and the output value from the constant setting circuit 10, and if the value of the output from the counting circuit 8 is larger than the value set in the constant setting circuit 10, the glass body 1- It is determined that a finger is placed on the finger 1 and outputs an entire area scanning start signal to the mechanical drive circuit 4. by this,
Fingerprint image input begins.

Next, the fingerprint image input operation will be explained. When the mechanical drive circuit 4 receives the entire area scanning start signal.

A drive pulse is sent to the pulse motor 1-4 in the fingerprint detection section 1 to cause the fingerprint detection section 1 to perform sub-scanning over the entire scanning area. Through this operation, a fingerprint image is captured and an image signal is output. The output image signal is quantized by the A/D conversion circuit 5 and stored in the storage circuit 11. Furthermore, the image data stored in the storage circuit 11 is sent to a host computer (not shown) via an interface 12.

In addition, in the above-mentioned embodiment, the glass body 1-
1 was used, but it is also possible to use transparent curved plastic in the same way.

[Effects of the Invention] As explained above, the present invention uses a transparent body in which the force wall surface and the outer wall surface are the same cylindrical surface for the fingerprint imprinting part, so that the input image area is wider than when using a prism. 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 input one image.

Furthermore, by applying a transparent elastic thin film to the wall of the vitreous body, high adhesion between the ridges and the stamping surface can be obtained, so that a clear gradation image 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 human-powered image device using a prism, Fig. 3 is a principle diagram for explaining the principle of detecting an image using the device shown in Fig. 2, and Fig. 4 is a fingerprint of the present invention. FIG. 5 is a perspective view of the detection section, FIG. 5 is a partial sectional view of the fingerprint detection section of FIG. 4, and FIG. 6 is a diagram showing the range of preliminary sub-scanning. 1... Fingerprint detection unit, 2... Sensor drive circuit, 3...
- Preliminary scanning control circuit, 4... mechanical drive circuit, 5, 23
... A/D conversion circuit, 6, 9... Comparison circuit, 7, 1
0...constant setting circuit, 8...counting circuit, 11.24
...Memory circuit, 12.28...Interface,
1-1... Glass body, 1-2... One-dimensional image sensor, 1-3... Illumination section, 1-4... Pulse motor, 1-5... Support stand, 1-7 ...transparent elastic thin film,
1-10... Finger, 20... Prism, 21... Light source, 22... Detection unit, 25... Monitor, 26...
Keyboard, 27...Control Figure 5 Figure 6 CC'

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; an illumination means that illuminates the imaging area of the one-dimensional image sensor; and a total reflection condition for directing the one-dimensional image sensor and the illumination means against the inner wall surface. a sub-scanning means for performing sub-scanning of the one-dimensional image sensor along the outer wall surface while maintaining the total reflection condition; Binarization means for converting into a binarized image signal based on a set threshold;
1 of the image signal every predetermined number of main scans.
” or “0” frequency and outputs a counted value; and when detecting that the counted value exceeds a predetermined setting value, output means outputs a full area scanning start signal. , when the one-dimensional image sensor starts main scanning, it controls the sub-scanning means every predetermined number of main scans to repeatedly perform sub-scanning, and when the one-dimensional image sensor receives the full-area scanning start signal, An image input device comprising: control means for controlling the sub-scanning means to perform sub-scanning over the entire imaging area.