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Fingerprint Sensing device using pulse processing

[Category : - Computers and computer accessories - Security and alarms- Indentification and payment methods]
[Viewed 2009 times]

A fingerprint sensing device that measures the capacitance between an array of electrode plates and finger skin using pulse processing, in which pulse width rather than voltage level, is used for capacitance measurement and digital signal conversion. A pulse, the width of which is compared and adjusted with that of a reference pulse, is generated when voltage at sensing electrodes in discharging is compared with a reference voltage. The comparison results are then digitalized in a grade image sensor or output directly in a binary image sensor. The sensor can communicate with a CPU using serial communication, parallel communication, or memory map scheme. Since no A/D is used, there is no extra time and hardware cost for the conversion from analog signals to digital signals. Due to the pulse processing nature, the circuits can be configured insensitive to the change or fluctuation in voltage supply. This feature enables the sensing device work with a variety of voltages, and thus it can be better used in portable, battery powered or passive devices.


Financial information

- what you are looking for ?
I am looking for an outright sale, exclusive license with right to enforce, exclusive license, non-exclusive license, region/country license, and/or field-of-use license.


- whether your invention has been previously sold or marketed?
No, it was not sold before.

- what is the market potential?
This invention provides a new feature which enables a low cost fingerprint sensing device to work at a variety of voltages, and thus it can be better used in portable, battery powered or passive devices. According to a research report of the Global Information Inc (GII), the global market for silicon-based fingerprint sensors is projected to reach $255 million by 2018. Major players in this market include Atmel Corporation, AuthenTec Inc., Fingerprint Cards AB, Fujitsu Limited, Hangzhou Synochip Technologies Co. Ltd., IDEX ASA, Jiangsu Winch Corp. Ltd., Validity Sensors Inc., among others. (Link)

1. Overview
This patent is about a fingerprint sensing device that measures the capacitance between an array of electrode plates and finger skin using pulse processing, in which pulse width rather than voltage level, is used for capacitance measurement and digital signal conversion. A pulse, the width of which is compared and adjusted with that of a reference pulse, is generated when voltage at sensing electrodes in discharging is compared with a reference voltage. The comparison results are then digitized in a grade image sensor or output directly in a binary image sensor. In the signal sensing and digitizing process, no Analog to Digital Conversion (ADC) is used. Therefore, the sensing circuit is simplified and both of the energy cost and the overall sensing time are decreased. Furthermore, due to the pulse processing nature, the circuits can be configured insensitive to the change or fluctuation in voltage supply. This feature enables the sensing device work with a variety of voltages, and thus it can be better used in portable, battery powered or passive devices.

2. Primary Application of the Technology

This invention provides a fingerprint sensing method without Analog-to-Digital conversion.
This technology simplifies sensing circuit, lowers energy cost, and shortens overall sensing time. It can be primarily used in fingerprint sensors, especially the fingerprint sensors requiring low energy cost or longer battery lasting life, such as that in smart phones. Moreover, since the pulse-processing in this invention enables fingerprint image sensing insensitive to the change or fluctuation in voltage supply, this technology also allows applications with varying voltage supply. One such application is RFID fingerprint sensing, in which fingerprint is sensed in an RFID tag and the sensing information is read through an RFID interrogator or reader. The RFID fingerprint sensing can be used in security cards and credit cards. Different from other devices that need a fingerprint sensor at the reader side and a fingerprint sensing process, the security cards or credit cards with RFID fingerprint sensing reads fingerprint at the tag side, and fingerprints are sensed as long as one hold the sensing area of the card.

3. The Problem Solved by the Technology

Normally, the sensing process for capacitive fingerprint sensors includes capacitance sensing and Analog to Digital (A/D) conversion. In capacitance sensing, an electrical level signal is generated for the capacitance of each sensing point, and then with an A/D converter the level signals are converted to digital signals which can be accessed by a CPU through a communication circuit. In this process, the capacitance sensing and the A/D conversion can be independent. The overall fingerprint sensing speed is limited by capacitance sensing speed, scanning frequency, communication bandwidth, and A/D conversion sampling rate. Normally it needs a few seconds to obtain a good fingerprint image. Also, A/D conversion needs a precise reference voltage, which requires a stable voltage supply.

4. How the Technology Solves the Problem

In this invention, the sensing circuit converts the capacitance value of each sensing point directly into digital signals with a pulse-processing method rather than using A/D conversion. The pulse-processing by nature is simple, inexpensive, and resistive to noises. And since digitization and capacitance sensing are completed simultaneously in one pulse, no extra time is needed for generating analog level signals and converting the level signals to digital signals, resulting in fast sensing. Additionally, by using the pulse-processing method, no voltage level signal is employed for comparison and reference. Therefore, the circuits in the present invention can be configured insensitive to the change or fluctuation in voltage supply. This feature enables the sensing device work with a variety of voltages, and thus it can be better used in portable, battery powered or passive devices.

5. Competitive Advantage

1. Simplified sensing circuit;
2. Lower energy cost or longer battery lasting life;
3. Shorter overall sensing time;
4. Insensitive to varying voltage supply.


- whether you have specific conditions for the sale?
N/A

- whether you have other pieces of intellectual property associated with your invention?
US Patent 7,965,877.







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