JP2006149634A - Biological information detector for finger and biological information authentication apparatus for same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve miniaturization and cost reduction while keeping easiness to correlate partial fingerprint images at a fingerprint sensor, and to reduce shading. <P>SOLUTION: The fingerprint sensor has a pixel area in which pixels 15 are arranged two-dimensionally and photographs a partial image of a finger print while moving the finger on the pixel area, wherein the density of the number of pixels in a moving direction of the finger in the pixel area is made different from that in a direction vertical to the moving direction of the finger to reduce the number of pixels while keeping the width of the pixel area with respect to the moving direction of the finger. In an optical-type finger print sensor, the pixel has larger opening part as the pixel more away from an LED, thereby shading is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a biometric information detection apparatus and biometric information authentication apparatus that detect biometric information of a finger such as a blood vessel pattern of a finger or a fingerprint, and in particular, to capture a partial image of the biometric information of a finger while moving the finger. The present invention relates to a biometric information detection apparatus and a biometric information authentication apparatus.

  Authentication apparatuses for authenticating biometric information such as finger blood vessel patterns and fingerprints, particularly fingerprint authentication apparatuses, have been applied to mobile phones and the like, and downsizing of the image sensor portion, which is a biometric information input apparatus, is important. Therefore, a method of obtaining a fingerprint image by moving (sweeping) a finger on a sensor as in Patent Document 1 is used.

In such a sweep type sensor, while the finger is swept, a partial image of the fingerprint is continuously photographed to obtain an image for the entire fingerprint. In this way, it is not necessary to secure a pixel area that can accommodate the entire finger.
In the fingerprint authentication device, there are two types of methods for processing the fingerprint partial image acquired by the sweep sensor. One is a method of detecting the overlapping part (correlated part) of the preceding and following images, and reconstructing the entire image of the fingerprint by connecting the preceding and succeeding images so that only one image is used for that part. Then, fingerprint verification is performed by a method such as feature point extraction. The other is a method of performing frequency analysis from the acquired fingerprint partial image without performing reconstruction.

  However, in the case of the current sweep type sensor, in particular, one using an optical sensor as in Patent Document 1, the area occupied by the pixel portion and the memory portion is large, and the entire sensor has become large.

  One possible way to reduce the size is to reduce the number of pixels and memory. Reducing the number of pixels and memories contributes to miniaturization not only for optical sensors but also for capacitive sensors. However, if the length of the pixel region in the sweep direction is shortened in the sweep type sensor, there is a problem that it becomes difficult to correlate the images before and after reconstruction when the finger sweep speed is high.

Also, when performing frequency analysis without reconstructing, if the length of the pixel region in the sweep direction is short, the fingerprint information included in each fingerprint partial image is small, which makes analysis difficult.
Japanese Patent Laid-Open No. 2003-242489

  In the present invention, while effectively utilizing the space in the sensor, maintaining high ease of correlation and sensitivity when reconstructing the image, and maintaining a large amount of information included in the fingerprint partial image when performing frequency analysis, An object of the present invention is to provide a device that realizes downsizing and cost reduction.

  Another object of the present invention is to reduce shading by adjusting the size of a pixel opening in an optical sensor.

In order to achieve the first object, the present invention has a region in which pixels are two-dimensionally arranged, and a partial image of finger biometric information is photographed while moving the finger over the region. In the finger biometric information detection device,
There is provided a biological information detecting apparatus, wherein a pixel number density in a moving direction of a finger in the region is different from a pixel number density in a direction perpendicular to the moving direction of the finger.

  In order to achieve the second object, in the present invention, the finger is irradiated with the light emitted from the light emitting means, and the biological information image of the finger is arranged in a two-dimensional manner by the transmitted light or reflected light from the finger. In the living body information detecting apparatus for reading in a region, a living body information detecting apparatus in which the pixel opening of the pixel is enlarged as the distance from the light emitting means increases.

  The biometric information of the finger typically includes a finger blood vessel pattern and a fingerprint.

  According to the present invention, in the sweep-type finger biometric information detection apparatus, it is possible to realize downsizing and cost reduction of the sensor while maintaining easy correlation between partial images of biometric information. Further, in the biological information detection apparatus that reads the biological information of the finger optically, shading can be reduced by adjusting the size of the pixel opening.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate, taking an optical sweep sensor as an example. In the following description, an optical sensor will be described as an example. However, the present invention is not limited to an optical sensor, and can be applied to a capacitive sweep sensor. In the following description, a fingerprint is taken up as biometric information, but a blood vessel pattern may be used.

  FIG. 1 is a block diagram showing a configuration of a fingerprint authentication apparatus having an optical sweep sensor. FIG. 17 is an explanatory diagram showing the movement of the finger with respect to the sensor unit.

  When the finger movement (sweep) is started as shown in FIG. 17, imaging of the fingerprint partial image 10 is started in the pixel unit 2. The fingerprint partial image 10 is temporarily held in the frame memory unit 3 in the sensor unit 1 serving as a fingerprint sensor device (biological information detection device), and then stored in the memory unit 6 in the microcomputer unit 5 through the AD converter 4. This operation is performed n times until the finger sweep is completed, and fingerprint partial images 10 for n frames are photographed. These fingerprint partial images 10 are sequentially stored in an arbitrary memory in the memory unit 6. For example, the first frame is stored in the memory I, the second frame is stored in the memory II, and the nth frame is stored in the memory n. The sensor unit 1 and the microcomputer unit 5 constitute a fingerprint authentication device (biological information authentication device).

  The frame memory unit 3 in the sensor unit 1 is for shortening the time from the start to the end of photographing one frame. Since the sweep sensor photographs a moving finger, it is important to shorten this time.

  The n fingerprint partial images 10 are sent to the image processing unit 7 where image reconstruction, image enhancement, and the like are performed. The fingerprint composite image 11 obtained by reconstruction here is stored in the fingerprint database 8 or collation with a fingerprint stored in advance in the fingerprint database 8 is performed in the collation unit 9.

FIG. 2 simply shows the circuit configuration of the pixel unit 2 of the optical sweep sensor, the unit pixel in the frame memory unit 3, and the unit frame memory. The unit pixel includes a photodiode PD, a switch M _TX for transferring the signal charge of the photodiode PD to the subsequent amplifier M _SF , a reset switch M _RES for removing residual charge in the gate part of the amplifier M _SF , and a signal of the gate part An amplifier M _SF that buffers the voltage, and a selection switch M _SEL that controls reading of the output from the amplifier M _SF to the signal line. A pixel configuration including such an amplifier is a pixel configuration called a CMOS sensor. In this embodiment, the signal charge accumulated in the photoelectric conversion unit is applied to the control electrode (gate, base, etc.) of the transistor provided in the pixel. A sensor of a type that outputs a signal that is guided and amplified from a main electrode (drain or emitter) can be used in the pixel of this embodiment. Each transistor is not limited to a MOS transistor, and VMIS (Threshold Voltage Modulation Image Sensor), BCAST (Buried Charge Accumulator and Sensing Transistor array), LBCAST (Lateral Buried Charge Accumulator and Sensing Transistor array), and the like are also applicable. In particular, BCAST and LBCAST can be realized without substantial change by replacing the amplification MOS transistor with a JFET transistor. In addition, SIT type image sensor using SIT as an amplifying transistor (A. Yusa, J. Nishizawa et al., “SIT image sensor: Design consideration and characteristics,” IEEE trans. Vol. ED-33, pp.735- 742, June 1986.) BASIS using bipolar transistors (N. Tanaka et al., “A 310K pixel bipolar imager (BASIS),” IEEE Trans. Electron Devices, vol.35, pp. 646-652, may 1990) ), CMD using a JFET with a depleted control electrode (Nakamura et al. “Gate Storage Type MOS Phototransistor Image Sensor”, Television Society Journal, 41, 11, pp.1075-1082 Nov., 1987).

Reset noise of the photodiode signal and the pixel amplifier M _SF from the unit pixel, the capacitance C _S of the unit frame memory _is read after being temporarily stored respectively in the C _N. M ₁ and M ₂ are switches for controlling writing to the capacitors C _S and C _N , and M ₃ and M ₄ are switches for controlling reading from the capacitors C _S and C _N.

  FIG. 3 schematically shows images of the mth frame 12 and the m + 1th frame 13 of the fingerprint partial image 10. The reconstruction performed by the image processing unit 7 will be described with reference to FIG.

  The overlapping portion 14 of the image in FIG. 3 is a portion obtained by photographing the same place of the finger in the mth frame 12 and the m + 1th frame 13. The image processing unit 7 detects this portion between two consecutive images. When connecting the previous and next images, omit this part from either the m-th frame 12 or the m + 1-th frame 13 so that this overlapping part does not appear twice in the reconstructed image. Connect from.

  FIG. 15 schematically shows an arrangement of the pixels 15 and the frame memory 16 in the pixel unit 2 and the frame memory unit 3 in the sensor unit 1. Here, the sweep direction of the finger is defined as the vertical direction, and the direction perpendicular to the sweep direction is defined as the horizontal direction. Further, the arrangement of the vertical pixels 15 and the frame memory 16 is referred to as a column, and the arrangement of the horizontal pixels 15 and the frame memory 16 is referred to as a row. FIG. 15 shows an example having 12 pixel rows.

  In the sensor unit 1, the area occupied by the pixel unit 2 and the frame memory unit 3 is large. It is effective to reduce the number of pixels 15 and frame memory 16 in order to reduce the size and price of the sensor.

  Here, a case where 12 pixel rows are reduced to 6 is taken as an example. As a simple method, there is a method of arranging the pixels 15 and the frame memory 16 as shown in FIG.

  However, in the case of FIG. 16, the length of the pixel unit 2 in the sweep direction is shortened. This leads to difficulty in removing the overlapping portion 14 in the image of FIG. When the finger sweep speed is high, it is necessary to increase the operation speed of the sensor or shorten the exposure time in order to secure the overlapping portion 14 of the image as before the pixel reduction.

  Also, when performing frequency analysis without reconstructing, narrowing the pixel area results in less information contained in each fingerprint partial image when the finger is fast.

  Therefore, the fingerprint sensor device of the embodiment as described below is used.

Example 1
In Embodiment 1 of the present invention, the pixel density is different between the vertical direction and the horizontal direction, that is, the pixel density in the vertical direction is sparse so that the correlation between the previous and subsequent images is maintained and the pixel rows are maintained. To reduce size and price.

  Specifically, the pixels 15 and the frame memory 16 are arranged as shown in FIG. In this way, by increasing the pixel pitch in the vertical direction (sweep direction) compared to the horizontal direction (by reducing the pixel density in the vertical direction compared to the horizontal direction, in other words, the pixels in the pixel column with respect to the pixel row) By reducing the density), it is possible to maintain the vertical length of the pixel portion 2 as before the pixel reduction, and therefore maintain the same ease of correlation. In addition, simplification and cost reduction by reducing the number of pixels, and miniaturization by reducing memory rows are realized.

  In this case, the conventional resolution is maintained in the horizontal direction. Reducing the number of pixels in the horizontal direction does not directly contribute to miniaturization in the sweep direction (because pixel rows and memory rows do not decrease), so keeping the resolution high here is an effective use of space It becomes.

(Example 2)
In the second embodiment, the pixel pitch in the sweep (moving) direction is made non-uniform (the pixel number density in the sweep direction is non-uniformly distributed), thereby reducing the size while maintaining the ease of correlation. Realize low cost.

  Specifically, the pixel 15 and the frame memory 16 are arranged as shown in FIG. In the configuration of FIG. 5, the vertical pixel pitch has a dense portion and a sparse portion. Here, the pixel pitch is changed by not arranging the pixels for a plurality of pixel rows, but the pixel pitch can be set as necessary. For example, when the pixel pitch in FIG. From the sweep direction, the pixel pitch between the first pixel row and the second pixel row, the sixth pixel row and the frame memory is 0.5, the second pixel row and the third pixel row, the fifth pixel row and the sixth pixel row. It is also possible to set the pixel pitch to 1, the third pixel row to the fourth pixel row, and the fourth pixel row to the fifth pixel row to 1.5. As a whole, the pixel unit 2 maintains the same width in the vertical direction as before the reduction, and therefore maintains the same level of correlation. In addition, simplification and cost reduction by reducing the number of pixels and size reduction by reducing the number of memories are realized. As in the first embodiment, the conventional resolution is maintained in the direction perpendicular to the sweep direction.

(Example 3)
In the third embodiment, when the pixel density per unit length is changed vertically and horizontally, the pixel openings are made different in length and width to make the pixel openings as large as possible instead of the same as in the first embodiment. Try to take. This improves the sensitivity.

  Specifically, as shown in FIG. Since the length of the pixel opening in the vertical direction is longer than that in the first embodiment, higher sensitivity can be realized.

Example 4
In the fourth embodiment, in the sweep sensor in which the number of pixels is reduced as in the first and second embodiments, the frame memory 16 is arranged in a space where there is room between the pixel rows, thereby further reducing the size.

  Specifically, as shown in FIG. 7, the frame memory 16 is arranged between pixel rows each including an array of pixels 15, and as shown in FIG. 8, all the frame memories 16 are arranged between certain pixel rows. Further, one frame memory is arranged between the first pixel row and the second pixel row, the fifth pixel row and the sixth pixel row from the sweep direction, and the second pixel row, the third pixel row, and the fourth pixel row are arranged. A configuration in which two rows of frame memories are arranged between the pixel row and the fifth pixel row is also possible. Thereby, the magnitude | size of a sweep direction can be made still smaller than the case of Example 1,2.

(Example 5)
In the fifth embodiment, the frame memory 16 is arranged between the pixel columns, thereby realizing a reduction in size in the sweep direction.

  A case is assumed in which the arrangement shown in FIG. 15 is downsized. Specifically, the arrangement can be reduced as shown in FIG.

  In the example of FIG. 9, since the frame memory 16 is arranged between the pixels in the horizontal direction, the resolution is lowered only in the horizontal direction, but the number of pixels is also reduced in the vertical direction for further simplification and cost reduction. However, there is a method as shown in FIG. 10 (12 pixel rows are changed to 6 pixel rows) and a method of increasing the area of the frame memory 16 to stabilize the operation and as shown in FIG.

(Example 6)
In the sixth embodiment, in the optical fingerprint sensor having the light emitting means 17, the shading can be reduced by increasing the pixel opening as the pixel is farther from the light emitting means 17.

  FIG. 12 schematically shows this embodiment. As shown in FIG. 12, the size of the pixel opening is adjusted to be farther away from the light emitting means 17, and the size of the pixel opening is increased, and the sensitivity of the pixel farther from the light emitting means 17 such as an LED is increased. This corrects the shading of the sensor.

  FIG. 13 schematically shows the effect of opening correction. The horizontal axis is the distance from the LED to the pixel, and the vertical axis is the pixel output. The output signal before correction is, for example, as shown by the solid line in the figure, and the closer to the LED, the higher the output intensity. Correcting the size of the opening as shown in FIG. 12 has the effect of reducing the difference in output as indicated by the dotted line in the figure.

  The present embodiment is not particularly limited to a fingerprint sensor device that captures a partial image of a moving finger, but can also be applied to a fingerprint sensor device that captures an image of a finger while the finger is stationary.

(Example 7)
The configuration of the sixth embodiment can be appropriately combined with the configurations of the first to fifth embodiments. For example, in the seventh embodiment, by providing a fingerprint authentication device having both the configuration of the first embodiment and the configuration of the sixth embodiment, a fingerprint authentication device that realizes both miniaturization and shading reduction is provided. .

  Assume that the sensor having the arrangement of FIG. 15 is subjected to downsizing and shading correction. Specifically, as shown in FIG. 14, as the distance from the light emitting means 17 such as an LED increases, the size of the pixel opening is increased and the number of pixel rows is changed from 12 to 6 rows. Thereby, simplification and cost reduction by reducing the number of pixels, miniaturization by reducing the frame memory array, and shading correction by adjusting the size of the pixel opening are realized. In this case, the horizontal resolution is maintained at the same level as before the reduction.

  By mounting the fingerprint sensor device according to this embodiment alone on an information device such as a mobile phone, a PDA, a notebook PC (personal computer), or a stationary PC, a partial fingerprint image output from the fingerprint sensor device is displayed on the Internet. When the fingerprint authentication server performs fingerprint authentication like the microcomputer unit 5 in FIG. 1 and sends the information on whether or not to accept the fingerprint authentication to the information device through the communication line, and the fingerprint authentication is performed. It is also possible to take an authentication method that permits a mobile phone call, activation of PC application software, and the like. Of course, the fingerprint authentication apparatus as shown in FIG. 1 can be mounted on an information device such as a PDA, a notebook PC (personal computer), or a stationary PC.

  The present invention is applied to a biological information detection apparatus mounted on an information device such as a mobile phone, a PDA, a notebook PC (personal computer), or a stationary PC that requires personal authentication. Even when the biometric information authentication apparatus including the biometric information detection apparatus and an authentication unit that authenticates biometric information based on a plurality of partial images output from the biometric information detection apparatus is mounted on the information device described above, The invention applies.

It is the block diagram which showed the structure of one Embodiment of a fingerprint authentication apparatus. It is the figure which represented simply the circuit structure of the pixel of an optical sweep sensor. It is a schematic diagram showing the fingerprint partial image of the mth frame and the (m + 1) th frame. FIG. 16 is a schematic diagram illustrating an example in which pixel rows are reduced in a form in which the vertical and horizontal pixel pitches are different from the fingerprint sensor of FIG. 15. FIG. 16 is a schematic diagram illustrating an example in which pixel rows are reduced in a form in which the vertical pixel pitch is nonuniform with respect to the fingerprint sensor of FIG. 15. FIG. 5 is a schematic diagram illustrating an example in which the length of the pixel opening is different in length and breadth in order to make the pixel opening large with respect to the fingerprint sensor of FIG. 4. FIG. 5 is a schematic diagram illustrating an example in which a frame memory is arranged between pixel rows in the fingerprint sensor of FIG. 4 and the size is reduced in a sweep direction. FIG. 6 is a schematic diagram illustrating an example in which a frame memory is arranged between pixel rows and the size is reduced in a sweep direction with respect to the fingerprint sensor of FIG. 5. It is a schematic diagram which shows the example of the arrangement | sequence of a pixel and a frame memory of the fingerprint sensor which has arrange | positioned the frame memory between pixel rows. FIG. 10 is a schematic diagram illustrating an example in which the number of pixels in the vertical direction is reduced and the price is simplified and reduced with respect to the fingerprint sensor of FIG. 9. FIG. 11 is a schematic diagram showing an example in which the operation of the fingerprint sensor of FIG. 10 is made larger by increasing the area of the frame memory. It is a schematic diagram showing a pixel portion and a frame memory portion of a fingerprint sensor in which a pixel opening portion is enlarged as a pixel farther from the light emitting means and shading is reduced. It is the figure which represented typically the effect of the magnitude | size correction | amendment of a pixel opening part. 15 is a schematic diagram illustrating an example in which shading is reduced by reducing pixel rows in a form in which vertical and horizontal pixel pitches are different from those of the fingerprint sensor of FIG. FIG. It is a schematic diagram which shows an example of the arrangement | sequence of the pixel and frame memory in a common fingerprint sensor. FIG. 16 is a schematic diagram illustrating an example in which the pixel rows of the fingerprint sensor in FIG. 15 are simply reduced. It is explanatory drawing which shows the movement of the finger | toe with respect to a sensor part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor part 2 Pixel part 3 Frame memory part 4 AD converter 5 Microcomputer part (authentication part)
6 memory part 7 image processing part 8 fingerprint database 9 collation part 10 fingerprint partial image 11 fingerprint image after composition 12 mth frame 13 m + 1 frame 14 overlapping part of the image 15 pixels 16 frame memory 17 light emitting means

Claims (9)

In the finger biometric information detection device that has a region in which pixels are arranged two-dimensionally and shoots a partial image of the finger biometric information while moving the finger over the region,
The biological information detection apparatus according to claim 1, wherein a pixel number density in a moving direction of the finger in the region is different from a pixel number density in a direction perpendicular to the moving direction of the finger. The biological information detection apparatus according to claim 1, wherein the pixel number density in the moving direction of the finger is unevenly distributed. The biological information detection apparatus according to claim 1 or 2, wherein the length of the pixel opening in the direction of movement of the finger in the region is different from the length of the pixel opening in a direction perpendicular to the direction of movement of the finger. A biological information detection apparatus characterized by the above. The biological information detection apparatus according to claim 1 or 2, wherein the lengths of the pixel openings in the direction of movement of the finger are unevenly distributed. The biological information detection apparatus according to claim 1, wherein a pixel signal memory that holds an output signal from the pixel is arranged between pixel rows. The biological information detection apparatus according to claim 1, wherein a pixel signal memory that holds an output signal from the pixel is arranged between pixel columns. In a biological information detection apparatus that irradiates a finger with light emitted from a light emitting means and reads a biological information image of the finger with transmitted light or reflected light from the finger in a region in which pixels are arranged in a two-dimensional manner, the biological information detecting device is separated The biological information detection apparatus which enlarged the pixel opening part of the said pixel according to. The biological information detection apparatus according to any one of claims 1 to 6,
Irradiating the finger moving the light emission from the light emitting means, and reading the biological information image of the finger in the region by transmitted light or reflected light from the finger;
The biological information detection apparatus which enlarged the pixel opening part of the said pixel as it left | separated from the said light emission means. The biometric information detection apparatus according to any one of claims 1 to 8 and a plurality of partial images output from the biometric information detection apparatus to detect the characteristics of the biometric information of the finger, A biometric information authentication device having an authentication unit that authenticates information.