TWI698801B - Fingerprint image compensation method capable of adapting to different transparent cover layer thickness, transparent cover layer fingerprint recognition device and information processing device - Google Patents

Abstract

A fingerprint image compensation method that can adapt to different transparent cover layer thicknesses is realized by a control circuit and includes the following steps: a touch detection circuit is used to select a transparent cover layer of a capacitive fingerprint sensor A central sensing point in the sensing area sends out a pulse signal and captures the sensing values of a plurality of sensing points in the selected sensing area; using a processor to perform the sensing values of the plurality of sensing points Fourier transform to obtain a degraded model function; and use the processor to perform an inverse Fourier transform on the inverse of the degraded model function to obtain an enhanced operator function; wherein, the enhanced operator function is used for the capacitive fingerprint A fingerprint image measured by the sensor performs a convolution operation to obtain an enhanced image.

Description

Fingerprint image compensation method capable of adapting to different transparent cover layer thicknesses, transparent cover layer fingerprint identification device and information processing device

The invention relates to a fingerprint image compensation method, in particular to a fingerprint image compensation method that can adapt to different transparent cover layer thicknesses.

With the increasing popularity and vigorous development of mobile devices, the human-machine interface of the display has become more and more intelligent, and can provide more and more functions, including input operation functions such as touch and pressure sensing, as well as fingerprint recognition and sound Biometric features such as pattern recognition and iris recognition.

Among various biometric identification functions, in addition to the uniqueness and permanent invariance of the fingerprint features based on fingerprint identification, the required storage space is quite small. Each fingerprint feature only needs about 120 to 180 bytes (byte ), therefore, the fingerprint recognition function has been commonly used in various mobile devices. In addition, since capacitive fingerprint sensors can be thinned and miniaturized, many mobile devices have adopted capacitive fingerprint sensors to provide fingerprint recognition functions.

The principle of the capacitive fingerprint sensor is to convert the different capacitance values corresponding to the ridge and valley lines of a fingerprint into different analog voltages, and then perform analog-to-digital conversion on the analog voltages to form a fingerprint image data.

In addition, a general capacitive fingerprint sensor will be provided with a transparent cover layer for a fingerprint to press. However, the transparent cover layer will blur the captured fingerprint image, and the thicker the transparent cover layer, the image will become The more blurred.

In addition, the conventional technology generally uses filtering operators such as image enhancement algorithms or inverse filtering methods to obtain clear images when restoring blurred fingerprint images. However, because a fixed filter operator has different restoration effects on the fingerprint images obtained by transparent cover layers of different thicknesses, that is to say, a fixed filter operator cannot be applied to transparent cover layers of different thicknesses. . On the other hand, for a transparent cover layer with a specific thickness, there will be a corresponding filter operator to generate a clear image, while other filter operators will generate a less clear image.

Please refer to Figure 1a, Figure 1b and Figure 1c together, in which Figure 1a shows an original fingerprint image 10 collected by a transparent cover layer of a specific thickness; Figure 1b shows the use of a filtering operator to compare Figure 1a A fingerprint image 11 processed by the original fingerprint image 10; and FIG. 1c shows a fingerprint image 12 processed by another filtering operator on the original fingerprint image 10 of FIG. 1a. As shown in the figure, the fingerprint image 11 is clearer than the fingerprint image 12. Therefore, if a fixed filter operator is installed in the control chip, the resolution of the fingerprint image output will be inconsistent when facing transparent cover layers of different thicknesses.

In order to solve the aforementioned problems, a novel fingerprint image compensation method is urgently needed in the art.

One purpose of the present invention is to disclose a fingerprint image compensation method that can adapt to different transparent cover layer thicknesses, which can obtain an enhanced operator function corresponding to the transparent cover layer by measuring the spatial impulse response of the transparent cover layer Therefore, in actual operation, a fingerprint image blurred by the transparent cover layer is effectively restored to a clear fingerprint image.

Another object of the present invention is to disclose a capacitive fingerprint sensor that can measure the spatial impulse response of a transparent cover layer to obtain an enhanced operator function corresponding to the transparent cover layer before shipment. Therefore, in actual operation, a fingerprint image blurred by the transparent cover layer is restored to a clear fingerprint image by the corresponding enhancement operator function.

Another object of the present invention is to disclose an information processing device, which can effectively restore a fingerprint image blurred by a transparent cover into a clear fingerprint image by the aforementioned capacitive fingerprint sensor.

In order to achieve the aforementioned purpose, a fingerprint image compensation method that can adapt to different transparent cover layer thicknesses is proposed, which includes the following steps: a touch detection circuit is used to apply a touch detection circuit to a transparent cover layer of a capacitive fingerprint sensor. A central sensing point in the selected sensing area sends out a pulse signal and captures the sensing values of a plurality of sensing points in the selected sensing area; using a processor to measure the sensing values of the plurality of sensing points Perform Fourier transform to obtain a degenerate model function; and use the processor to perform an inverse Fourier transform on the inverse of the degenerate model function to obtain an enhanced operator function; wherein the enhanced operator function is used for the capacitive A fingerprint image measured by the fingerprint sensor performs a convolution operation to obtain an enhanced image.

In one embodiment, the touch detection circuit is a mutual capacitance touch detection circuit.

In a possible embodiment, the transparent cover layer is a transparent coating or a glass cover plate.

To achieve the foregoing objective, the present invention further provides a transparent cover fingerprint recognition device, which includes a capacitive fingerprint sensor, a touch detection circuit and a processor, wherein the processor is used to execute a fingerprint image Compensation method, the method includes the following steps:

The touch detection circuit is driven to send a pulse signal to a central sensing point of a selected sensing area of a transparent cover layer of the capacitive fingerprint sensor and to capture a plurality of sensors in the selected sensing area The sensing value of the measuring point;

Performing Fourier transform on the sensing values of the plurality of sensing points to obtain a degenerate model function; and

Perform an inverse Fourier transform on the reciprocal of the degradation model function to obtain an enhanced operator function; wherein, the enhanced operator function is used to perform a folding on a fingerprint image measured by the capacitive fingerprint sensor Product operation to obtain an enhanced image.

In one embodiment, the touch detection circuit may be a mutual capacitance touch detection circuit.

In a possible embodiment, the transparent cover layer may be a transparent coating layer or a glass cover plate.

To achieve the foregoing objective, the present invention further provides an information processing device having a central processing unit and the aforementioned transparent cover fingerprint identification device, wherein the central processing unit is electrically coupled to the processor.

In a possible embodiment, the information processing device may be a smart phone or a portable computer.

In order to enable your reviewer to further understand the structure, features and purpose of the present invention, the drawings and detailed descriptions of preferred specific embodiments are attached.

Please refer to FIG. 2, which shows a flowchart of an embodiment of a fingerprint image compensation method adaptable to different transparent cover layer thicknesses of the present invention, wherein the fingerprint image compensation method is implemented by a control circuit.

As shown in FIG. 2, the fingerprint image compensation method includes the following steps: using a touch detection circuit to send a central sensing point of a selected sensing area of a transparent cover layer of a capacitive fingerprint sensor Pulse signal and capture the sensing values of the plurality of sensing points in the selected sensing area (step a); using a processor to perform Fourier transform on the sensing values of the plurality of sensing points to obtain a degradation model Function (step b); and use the processor to perform an inverse Fourier transform on the reciprocal of the degradation model function to obtain an enhanced operator function (step c); wherein, the enhanced operator function is used for the capacitive A fingerprint image measured by the fingerprint sensor performs a convolution operation to obtain an enhanced image.

In addition, the touch detection circuit can be a mutual capacitance touch detection circuit; the transparent cover layer can be a transparent coating or a glass cover.

The principle of the present invention is as follows:

In the process of fingerprint sensing, the original clear fingerprint image f(x,y) becomes a fuzzy fingerprint image g(x,y) due to the influence of a glass cover, where f(x, The Fourier transform function F(u, v) of y) and the Fourier transform function G(u, v) of g(x,y) can be expressed as

G(u,v) = H(u,v)‧F(u,v) (1).

In formula (1), H(u, v) represents a degradation model function generated by the glass cover, and it is obtained by Fourier transforming a spatial impulse response of the glass cover. After the degradation model function H(u,v) is obtained, an enhanced operator function c(x,y) can be obtained by performing an inverse Fourier transformation on the inverse of the degradation model function H(u,v), and After the enhanced operator function c(x,y) is obtained, the enhanced operator function c(x,y) and the fuzzy fingerprint image g(x,y) can be used to perform a convolution operation to obtain The original fingerprint image f(x,y), where the spatial frequency domain corresponding operation formula of the convolution operation can be expressed as

C(u,v)‧G(u,v) = C(u,v)‧〔H(u,v)‧F(u,v)] = 〔1/H(u,v)〕‧H( u,v)‧F(u,v)=F(u,v)(2).

In other words, by obtaining the degradation model function H(u, v) of the transparent cover layer of different thicknesses to generate different enhancement operator functions c(x, y), and use the enhancement operator functions c(x, y) Performing a convolution operation on the fuzzy fingerprint image g(x, y), the present invention can provide an adaptive fingerprint image compensation with a set of fixed algorithms and degradation model functions with different transparent cover thicknesses effect.

Based on the above description, the present invention provides a transparent cover fingerprint identification device. Please refer to FIG. 3, which shows a block diagram of an embodiment of the transparent cover fingerprint identification device of the present invention. As shown in FIG. 3, a transparent cover fingerprint recognition device 100 includes a capacitive fingerprint sensor 110, a touch detection circuit 120 and a processor 130.

The processor 130 is used to execute a fingerprint image compensation method, which includes the following steps: a selection of a transparent cover layer (not shown in the figure) of the capacitive fingerprint sensor 110 using the touch detection circuit 120 A central sensing point in the sensing area sends out a pulse signal and captures the sensing values of a plurality of sensing points in the selected sensing area; the processor 130 is used to perform processing on the sensing values of the plurality of sensing points Fourier transform to obtain a degraded model function; and use the processor 130 to perform an inverse Fourier transform on the reciprocal of the degraded model function to obtain an enhanced operator function; wherein the enhanced operator function is used to sense capacitive fingerprints A fingerprint image measured by the detector 110 performs a convolution operation to obtain an enhanced image.

In addition, the touch detection circuit 120 can be a mutual capacitance touch detection circuit, and the transparent cover layer can be a transparent coating or a glass cover.

Based on the above description, the present invention further provides an information processing device. Please refer to FIG. 4, which shows a block diagram of an embodiment of the information processing device of the present invention. As shown in FIG. 4, an information processing device 200, which can be a smart phone or a portable computer, has a central processing unit 210 and a transparent cover fingerprint recognition device 100 as shown in FIG. 3, wherein the central The processing unit 210 is electrically coupled to the processor 130.

With the design disclosed above, the present invention has the following advantages:

1. The fingerprint image compensation method of the present invention can obtain an enhanced operator function corresponding to the transparent cover layer by measuring the spatial impulse response of a transparent cover layer, so that it will be blurred by the transparent cover layer in actual operation The transformed fingerprint image is effectively restored to a clear fingerprint image.

2. The transparent cover fingerprint identification device of the present invention can measure the spatial impulse response of a transparent cover to obtain an enhanced operator function corresponding to the transparent cover before shipment, so that it can be used in actual operation. The corresponding enhancement operation sub-function restores a fingerprint image blurred by the transparent cover layer into a clear fingerprint image.

3. The information processing device of the present invention can effectively restore a fingerprint image blurred by a transparent cover into a clear fingerprint image by using the aforementioned capacitive fingerprint sensor.

The disclosure of the present invention is a preferred embodiment, and any partial changes or modifications that are derived from the technical idea of the present invention and can be easily inferred by those familiar with the art will not depart from the scope of the patent right of the present invention.

In summary, the purpose, means and effects of this invention show that it is very different from the conventional technology, and its first invention is suitable for practicality, and it does meet the requirements of a patent for the invention. I sincerely ask your examiner to check it out and grant the patent as soon as possible. To benefit society is to pray for the most.

10 Original fingerprint image 11, 12 Fingerprint image 100 Transparent cover fingerprint recognition device 110 Capacitive fingerprint sensor 120 Touch detection circuit 130 Processor 200 Information processing device 210 Central processing unit Step a--Using a touch detection The sensing circuit sends a pulse signal to a central sensing point in a selected sensing area of a transparent cover of a capacitive fingerprint sensor and captures the sensing values of a plurality of sensing points in the selected sensing area Step b—Using a processor to perform Fourier transform on the sensing values of the plurality of sensing points to obtain a degraded model function. Step c—Using the processor to perform an inverse Fourier transform on the inverse of the degraded model function to obtain An enhanced operator function

Fig. 1a shows an original fingerprint image collected by a transparent cover layer of a specific thickness. FIG. 1b shows a fingerprint image processed by a filter operator on the original fingerprint image of FIG. 1a. FIG. 1c shows a fingerprint image processed by another filter operator on the original fingerprint image of FIG. 1a. 2 shows a flowchart of an embodiment of a fingerprint image compensation method that can adapt to different transparent cover layer thicknesses according to the present invention. FIG. 3 is a block diagram of an embodiment of the transparent cover fingerprint identification device of the present invention. FIG. 4 shows a block diagram of an embodiment of the information processing device of the present invention.

Step a—Using a touch detection circuit to send a pulse signal to a central sensing point of a selected sensing area of a transparent cover layer of a capacitive fingerprint sensor and to capture plural numbers in the selected sensing area Step b-use a processor to perform Fourier transform on the sensing values of the plurality of sensing points to obtain a degradation model function Step c-use the processor to reciprocate the degradation model function Perform an inverse Fourier transform to obtain an enhanced operator function

Claims (8)

A fingerprint image compensation method that can adapt to different transparent cover layer thicknesses is realized by a control circuit and includes the following steps: A touch detection circuit is used to select a transparent cover layer of a capacitive fingerprint sensor A central sensing point in the sensing area sends out a pulse signal and captures the sensing values of a plurality of sensing points in the selected sensing area; using a processor to perform the sensing values of the plurality of sensing points Fourier transform to obtain a degraded model function; and use the processor to perform an inverse Fourier transform on the reciprocal of the degraded model function to obtain an enhanced operator function; wherein, the enhanced operator function is used for the capacitive fingerprint A fingerprint image measured by the sensor performs a convolution operation to obtain an enhanced image. As described in the first item of the scope of patent application, the fingerprint image compensation method that can adapt to different transparent cover layer thicknesses, wherein the touch detection circuit is a capacitive touch detection circuit. The fingerprint image compensation method that can adapt to different transparent cover layer thicknesses as described in item 1 of the scope of patent application, wherein the transparent cover layer is a transparent coating or a glass cover. A transparent cover fingerprint recognition device, which includes a capacitive fingerprint sensor, a touch detection circuit, and a processor, wherein the processor is used to execute a fingerprint image compensation method, and the method includes the following steps: The touch detection circuit is driven to send a pulse signal to a central sensing point of a selected sensing area of a transparent cover layer of the capacitive fingerprint sensor and to capture a plurality of sensors in the selected sensing area The sensing value of the measuring point; Fourier transforming the sensing values of the plurality of sensing points to obtain a degenerate model function; and Carrying out an inverse Fourier transform to the inverse of the degenerate model function to obtain an enhanced operator function ; Wherein, the enhanced operator function is used to perform a convolution operation on a fingerprint image measured by the capacitive fingerprint sensor to obtain an enhanced image. For the transparent cover fingerprint identification device described in the scope of patent application, the touch detection circuit is a mutual capacitance touch detection circuit. The transparent cover fingerprint identification device described in item 4 of the scope of patent application, wherein the transparent cover is a transparent coating or a glass cover. An information processing device has a central processing unit and the transparent cover fingerprint identification device as described in any one of items 4-6 in the scope of patent application, wherein the central processing unit is electrically coupled to the processor. For example, the information processing device described in item 7 of the scope of patent application is a smart phone or a portable computer.

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