Fingerprint detection system and method

Abstract

A fingerprint detection system and method are disclosed. The fingerprint detection system includes a fingerprint module configured to receive a fingerprint drive signal and perform a frequency modulation on the fingerprint drive signal to output a fingerprint signal having a first frequency in response to the fingerprint drive signal; and a signal processing circuit coupled to the fingerprint module and configured to receive the fingerprint signal having the first frequency, perform a frequency demodulation to shift the fingerprint signal from the first frequency to a second frequency, and filter the fingerprint signal having the second frequency in response to the first frequency, wherein the filtered fingerprint signal is used for fingerprint data analysis.

Description

TECHNICAL FIELD

[0001] The present application relates to a fingerprint detection system, and more particularly to a fingerprint detection system capable of removing noise by frequency modulation. BACKGROUND

[0002] With the advancement of technology, various types of mobile devices, such as smart phones, tablets, laptops, GPS navigator systems, and electronic books, have become an indispensable part of people's lives. Unlike traditional phones that only have a calling function, today's mobile devices integrate communication, networking, photography, gaming, data processing, and other functions together. The multi-functional design makes mobile devices more popular with consumers. Fingerprint recognition is a common function used to handle security and privacy issues. For example, a mobile phone can have a fingerprint recognition module built into the home button or a specific area (such as a sensor pad) that can be used to detect the user's fingerprint.

[0003] In recent years, optical fingerprint detection has become one of the most popular fingerprint detection solutions. Please refer to Figure 1 , Figure 1 is a schematic diagram of a fingerprint detection system 10. The fingerprint detection system 10 includes a fingerprint module and a readout integrated circuit (ROIC). In addition, the fingerprint module also includes a sensor pad for contacting a user's finger and sensing light reflected by the finger. In the detailed operation of fingerprint detection, a "Reset" signal can be used for resetting, and the fingerprint module can receive a fingerprint driving signal "Write" to enable the detection function of the fingerprint module, and then generate a fingerprint signal (which can be considered as the reflected light of the finger) including fingerprint information according to the "Write" signal and the sensing signal. The fingerprint signal is then transmitted to the readout integrated circuit ROIC for signal processing (such as noise removal and analog-to-digital conversion, etc.) for fingerprint data analysis. It should be noted that the fingerprint driving signal input to the fingerprint module is usually a direct current signal (i.e. a base frequency signal), so that the fingerprint signal output by the fingerprint module is also a direct current signal, which is easily disturbed by low frequency noise (such as flicker noise and thermal noise in the fingerprint module). In this way, when the readout integrated circuit ROIC receives the fingerprint signal from the fingerprint module, since the fingerprint signal and these noises are all in the low frequency range, it is difficult for the readout integrated circuit ROIC to remove these noises from the fingerprint signal.

[0004] In addition, the fingerprint detection system 10 is susceptible to interference from other modules in the mobile device. For example, if the fingerprint detection system 10 is integrated with a display module (e.g., an organic light-emitting diode (OLED) panel), the panel structure of the display module will affect the fingerprint signal on the fingerprint module, for example, the display module can also reflect some light. In other words, the coexistence of the fingerprint detection operation with the touch sensing and / or display operation will generate non-negligible interference on the fingerprint signal, which greatly increases the difficulty of fingerprint recognition. SUMMARY

[0005] Therefore, one of the purposes of the present application is to provide a fingerprint detection system to solve the above problems.

[0006] An embodiment of the present application discloses a fingerprint detection system. The fingerprint detection system includes a fingerprint module configured to receive a fingerprint driving signal and perform a frequency modulation on the fingerprint driving signal to output a fingerprint signal having a first frequency according to the fingerprint driving signal; and a signal processing circuit coupled to the fingerprint module and configured to receive the fingerprint signal having the first frequency, perform a frequency demodulation to shift the fingerprint signal from the first frequency to a second frequency, and filter the fingerprint signal having the second frequency according to the first frequency, wherein the filtered fingerprint signal is used for fingerprint data analysis.

[0007] Another embodiment of the present application discloses a fingerprint detection system. The fingerprint detection system includes a frequency modulation circuit configured to receive a fingerprint driving signal and perform a frequency modulation on the fingerprint driving signal to output the fingerprint driving signal having a first frequency; a fingerprint module configured to receive the fingerprint driving signal having the first frequency and output a fingerprint signal having the first frequency according to the received fingerprint driving signal; and a signal processing circuit coupled to the fingerprint module and configured to receive the fingerprint signal having the first frequency, perform a frequency demodulation to shift the fingerprint signal from the first frequency to a second frequency, and filter the fingerprint signal having the second frequency according to the first frequency, wherein the filtered fingerprint signal is used for fingerprint data analysis.

[0008] Another embodiment of the present application discloses a method for detecting a fingerprint for a fingerprint detection system. The method comprises receiving a fingerprint drive signal; performing a frequency modulation on the fingerprint drive signal to output the fingerprint drive signal with a first frequency; generating a fingerprint signal with the first frequency according to the fingerprint drive signal with the first frequency; performing a frequency demodulation on the fingerprint signal with the first frequency to shift the fingerprint signal from the first frequency to a second frequency; filtering the fingerprint signal with the second frequency according to the first frequency; and converting the fingerprint signal with the second frequency from an analog signal to a digital signal for fingerprint data analysis. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 Fig. 1 is a schematic diagram of a prior art fingerprint detection system.

[0010] Figure 2 Fig. 2 is a schematic diagram of a fingerprint detection system according to an embodiment of the present application.

[0011] Figure 3 Fig. 3 is a schematic diagram of a fingerprint detection system according to another embodiment of the present application.

[0012] Figure 4 Fig. 4 is a schematic diagram of the operation of a fingerprint detection system according to an embodiment of the present application.

[0013] In the drawings, the following reference numerals are used:

[0014] 10, 20, 30 fingerprint detection system

[0015] Reset signal

[0016] Write, Write fs fingerprint drive signal

[0017] ROIC readout integrated circuit

[0018] 200, 300 fingerprint module

[0019] 210, 310 signal processing circuit

[0020] f1 first frequency

[0021] f2 second frequency

[0022] fs frequency

[0023] 301 frequency modulation circuit

[0024] 40 signal processing procedure

[0025] 400-450 steps DETAILED DESCRIPTION

[0026] Please refer to Figure 2 , Figure 2 Fig. 1 is a schematic diagram of a fingerprint detection system 20. The fingerprint detection system 20 includes a fingerprint module 200 and a signal processing circuit 210 coupled to the fingerprint module 200. The fingerprint module 200 can receive a fingerprint driving signal "Write" to enable the fingerprint detection function, and then perform frequency modulation on the fingerprint driving signal to shift the fingerprint driving signal from a base frequency to a first frequency f1 (e.g., a frequency higher than the base frequency), so as to avoid interference in the base frequency range. In addition, the fingerprint module 200 includes a sensor pad 202 for detecting light reflected from a user's fingerprint, and the fingerprint module 200 generates a fingerprint signal having the first frequency f1 according to the received "Write" signal and the signal detected by the sensor pad 202. The signal processing circuit 210 can receive the fingerprint signal having the first frequency f1 from the sensor pad 202 of the fingerprint module 200, and perform frequency demodulation to shift the fingerprint signal from the first frequency f1 to a second frequency f2 (i.e., the base frequency). In addition, the signal processing circuit 210 can filter the fingerprint signal having the second frequency f2 according to the first frequency f1, so as to remove unnecessary noise at the first frequency f1.

[0027] In short, the "Write" signal input to the fingerprint module 200 can be modulated to the first frequency f1, which can be any frequency higher than the original frequency of the "Write" signal, so that the fingerprint signal output by the fingerprint module 200 is immune to low-frequency interference (e.g., noise from the fingerprint module 200 or other coexisting modules). On the other hand, the signal processing circuit 210 can demodulate the fingerprint signal having the first frequency f1 to the base frequency, and then filter out noise higher than the base frequency, so as to remove high-frequency interference.

[0028] It is noted that the interference mentioned herein can be any noise, which can include flicker noise and thermal noise of the fingerprint module 200 and any other module (e.g., display screen and touch screen) of an electronic device (e.g., mobile phone), but is not limited thereto.

[0029] The present disclosure aims to provide a signal processing method applicable to the fingerprint detection system 20. Those skilled in the art can modify or vary accordingly, without being limited thereto. For example, as shown in Fig. 2, the fingerprint module 200 can include a mixer (not shown in the figure) for mixing the "Write" signal (which can be a direct current signal) with a signal having a frequency fs, so as to generate a fingerprint driving signal "Write_fs" for the fingerprint module 200 to output a fingerprint signal having the frequency fs. In other embodiments, as shown in Fig. 3, the fingerprint module 200 can include a frequency generator 204 for generating a signal having the frequency fs, and a mixer (not shown in the figure) for mixing the "Write" signal (which can be a direct current signal) with the signal having the frequency fs, so as to generate a fingerprint driving signal "Write_fs" for the fingerprint module 200 to output a fingerprint signal having the frequency fs. Figure 2 Figure 2 It is noted that the fingerprint module 200 can include a mixer (not shown in the figure) for mixing the "Write" signal (which can be a direct current signal) with a signal having a frequency fs, so as to generate a fingerprint driving signal "Write_fs" for the fingerprint module 200 to output a fingerprint signal having the frequency fs. In other embodiments, as shown in Fig. 3, the fingerprint module 200 can include a frequency generator 204 for generating a signal having the frequency fs, and a mixer (not shown in the figure) for mixing the "Write" signal (which can be a direct current signal) with the signal having the frequency fs, so as to generate a fingerprint driving signal "Write_fs" for the fingerprint module 200 to output a fingerprint signal having the frequency fs.​Figure 3 The fingerprint detection system 30 shown may include a frequency modulation circuit 301, which is not integrated into the fingerprint module 300. This frequency modulation circuit 301 generates a "Write_fs" signal to be provided to the fingerprint module 300. On the other hand, the signal processing circuit 310 may include a mixer, a filter, and an analog-to-digital converter (ADC). The mixer mixes the received fingerprint signal at frequency fs with a signal at frequency fs, shifting the frequency of the fingerprint signal from fs to the fundamental frequency and shifting noise within the fundamental frequency range to frequency fs. Therefore, the filter removes noise based on frequency fs (i.e., any interference above frequency fs is removed), and then outputs a fingerprint signal with the fundamental frequency to the ADC, which converts the undisturbed fingerprint signal from an analog signal to a digital signal for fingerprint data analysis.

[0030] The above-described operation of the fingerprint detection system can be summarized as a signal processing flow 40, such as... Figure 4 As shown. Signal processing flow 40 can be implemented in Figures 2-3 The fingerprint detection system shown includes the following steps:

[0031] Step 400: Receive a fingerprint driving signal.

[0032] Step 410: Perform frequency modulation on the fingerprint driving signal to output a fingerprint driving signal with a first frequency.

[0033] Step 420: Generate a fingerprint signal with a first frequency based on the fingerprint driving signal with a first frequency.

[0034] Step 430: Perform frequency demodulation on the fingerprint signal with the first frequency to shift the fingerprint signal from the first frequency to the second frequency.

[0035] Step 440: Filter the fingerprint signal with the second frequency according to the first frequency.

[0036] Step 450: Convert the fingerprint signal with a second frequency from an analog signal to a digital signal for use in fingerprint data analysis.

[0037] According to signal processing flow 40, low-frequency noise in the fingerprint signal can be avoided and high-frequency noise can be removed, thereby obtaining a fingerprint signal with the required frequency and free from interference for fingerprint data analysis. For detailed explanations of the fingerprint detection system's operation, please refer to the preceding paragraphs; further details will not be elaborated here.

[0038] In summary, the present application can achieve noise removal of the fingerprint detection system to improve the reliability of fingerprint recognition. In detail, the fingerprint driving signal input to the fingerprint module can be modulated to high frequency to avoid low frequency noise, and the fingerprint signal output by the fingerprint module can be demodulated by the signal processing circuit to eliminate high frequency noise.

[0039] The above descriptions are only the preferred embodiments of the present application and are not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A fingerprint detection system, comprising: a fingerprint module configured to receive a fingerprint driving signal and perform a frequency modulation on the fingerprint driving signal to correspondingly output a fingerprint signal having a first frequency according to the fingerprint driving signal, wherein the fingerprint driving signal is a direct current signal, and the fingerprint module comprises a first frequency mixer configured to mix the fingerprint driving signal with a signal having the first frequency to generate the fingerprint signal having the first frequency; and a signal processing circuit coupled to the fingerprint module and configured to receive the fingerprint signal having the first frequency, perform a frequency demodulation to shift the fingerprint signal from the first frequency to a second frequency, and filter the fingerprint signal having the second frequency according to the first frequency, wherein the filtered fingerprint signal is used for fingerprint data analysis.

2. The fingerprint detection system of claim 1, wherein The signal processing circuit comprises a second frequency mixer, a filter, and an analog-to-digital converter, the second frequency mixer is configured to shift the received fingerprint signal from the first frequency to the second frequency and output the fingerprint signal having the second frequency to the filter to remove unnecessary noise on the fingerprint signal according to the first frequency, and then output to the analog-to-digital converter to convert the fingerprint signal having the second frequency from an analog signal to a digital signal for fingerprint data analysis.

3. The fingerprint detection system of claim 1, wherein The fingerprint driving signal is a direct current signal used to enable a fingerprint detection function.

4. The fingerprint detection system of claim 1, wherein The first frequency is any frequency higher than a frequency of the fingerprint driving signal.

5. The fingerprint detection system of claim 1, wherein The fingerprint module generates the fingerprint signal according to the fingerprint driving signal having the first frequency and a user's finger touch detected by an optical sensing method.

6. A fingerprint detection system, comprising: a frequency modulation circuit configured to receive a fingerprint driving signal and perform a frequency modulation on the fingerprint driving signal to output the fingerprint driving signal having a first frequency, wherein the fingerprint driving signal is a direct current signal, and the frequency modulation circuit comprises a first frequency mixer configured to mix the fingerprint driving signal with a signal having the first frequency to generate the fingerprint driving signal having the first frequency; a fingerprint module configured to receive the fingerprint driving signal having the first frequency and correspondingly output a fingerprint signal having the first frequency according to the received fingerprint driving signal; and a signal processing circuit coupled to the fingerprint module and configured to receive the fingerprint signal having the first frequency, perform a frequency demodulation to shift the fingerprint signal from the first frequency to a second frequency, and filter the fingerprint signal having the second frequency according to the first frequency, wherein the filtered fingerprint signal is used for fingerprint data analysis.

7. The fingerprint detection system of claim 6, wherein The signal processing circuit includes a second mixer, a filter and an analog-to-digital converter, the second mixer is used to shift the received fingerprint signal from the first frequency to the second frequency, and output the fingerprint signal with the second frequency to the filter to remove unnecessary noise on the fingerprint signal according to the first frequency, and then output to the analog-to-digital converter to convert the fingerprint signal with the second frequency from an analog signal to a digital signal for fingerprint data analysis.

8. The fingerprint detection system of claim 6, wherein The signal processing circuit is used to shift the fingerprint signal from the first frequency to the second frequency, and shift the noise of the second frequency to the first frequency.

9. The fingerprint detection system of claim 6, wherein The first frequency is any frequency higher than the frequency of the fingerprint driving signal received by the frequency modulation circuit.

10. The fingerprint detection system of claim 6, wherein The fingerprint module generates the fingerprint signal according to the fingerprint driving signal with the first frequency and the user's finger touch detected by an optical sensing method.

11. A method for detecting a fingerprint, for a fingerprint detection system, the method comprising: receiving a fingerprint driving signal; performing a frequency modulation on the fingerprint driving signal to output the fingerprint driving signal with a first frequency, wherein the fingerprint driving signal is a direct current signal, and a mixer is used to mix the fingerprint driving signal with a signal with the first frequency to generate the fingerprint driving signal with the first frequency; generating a fingerprint signal with the first frequency according to the fingerprint driving signal with the first frequency; performing a frequency demodulation on the fingerprint signal with the first frequency to shift the fingerprint signal from the first frequency to a second frequency; filtering the fingerprint signal with the second frequency according to the first frequency; and converting the fingerprint signal with the second frequency from an analog signal to a digital signal for fingerprint data analysis.

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