As each day brings increasing opportunities for fraud and greater needs for
security, biometric fingerprint sensors represent an attractive and convenient ...
Add Fingerprint Biometrics to Your Personal Authentication Application
A
s each day brings increasing opportunities for fraud and greater needs for security, biometric fingerprint sensors represent an attractive and convenient authentication method. In today’s networked world, there is no doubt that fingerprint biometrics will become an increasing part of everyday life, including personal authentication solutions.
fingerprint authentication to new designs. The reader hardware contains a high powered DSP processor that does all the image processing tasks and searching of fingerprint templates algorithms, leaving the Explorer 16 board’s microcontroller free for user application code.
Remarkable innovations in recent years have reduced the size, lowered the price, and improved sensor performance. These developments are making it possible to deploy fingerprint authentication beyond law enforcement to more widespread personal authentication applications. The Biometric Interface PICtail™ Board (Part # TSTEP001), developed by Electronicsteps—a trusted third party tool provider—is available today to assist you with your fingerprint authentication design. It can be attached to the Explorer 16 Development Board and it incorporates a fingerprint reader that uses a recognition algorithm that won an award in the worldwide Fingerprint Verification Competition (FVC).
Hardware Overview The Biometric Interface PICtail Board is a complete fingerprint interface solution combining a fingerprint reader module and a capacitive touch sensor in the same board, making it easy to add
Biometric Interface PICtail™ Board Part # TSTEP001
Electronicsteps provides the source code of the demo firmware in an MPLAB® X IDE-compatible project. It connects to the microcontroller by a simple serial interface, and sends packets of data to the module, allowing the user to easily enroll, delete and verify templates from fingerprints. The demo application is currently available for a PIC24FJ256GB110 PIM, but it’s very easy to migrate it to other families of devices.
The board was carefully designed to retain most of the Explorer 16 board’s expansibility to other Microchip PICtail boards, giving you the flexibility to expand your design to incorporate a more complex solution. For example, the Biometric Interface PICtail Board can be used in conjunction with a Graphics PICtail Board to quickly develop a time attendance solution that uses the display as a touch keybo ard. Or, an application can go mobile by connecting the Biometric Interface PICtail Board with the GSM Interface board from Electronicsteps. After prototyping a design with the Explorer 16 board plus the Biometric Interface PICtail Board, it’s very easy to move it to production. Electronicsteps can supply fingerprint modules in production volumes with 1–2 weeks lead time.
How It Works First, a fingerprint image is enrolled on the device used to perform the authentication and a template of the fingerprint is stored in the onboard Flash memory. When users want to verify their identity, they must have their enrolled finger scanned again, and a second template is generated. Next, a pattern analysis is performed to determine if there is a match. The match is determined using points of interest (minutia) on the fingerprint, such as ridge bifurcations and ridge endings. If enough of the minutia points and vectors match, the fingerprint is considered a match and the identity is confirmed. Fingerprint minutia points are extracted from an 8-bit high contrast grayscale image obtained by the capacitive sensor. Capacitive sensors use a difference between skinsensor and air-sensor contact in terms of capacitive values. When a finger is placed on the sensor, an array of pixels act as one plate of a parallel-plate capacitor, the dermal layer acts as the other plate, and the non-conductive epidermal layer acts as a dielectric. The capacitance varies between the ridges and valleys of the fingerprint due to the fact that the volume between the dermal layer and sensing element in valleys contains an air gap. The dielectric
constant of the epidermis and the area of the sensing element are known values. The measured capacitance values are then used to distinguish between fingerprint ridges and valleys resulting is an 8-bit high-contrast grayscale image.
Capacitive vs. Optical Sensors Capacitive sensors can provide significant advantages over optical sensors, such as reduced cost and power consumption. Also, the small form factor allows capacitive sensors to be integrated into portable devices, where an optical solution would be too large and less durable. Optical sensor technology creates patterns and images using light rather than current. Therefore, if the touch surface is scratched or stained, the captured image will be affected, potentially resulting in false mismatches. Also, the finger itself must be free of dirt, debris, and scratches. Capacitive sensors are not subject to these limitations, making them a much more practical option for fingerprint authentication applications. Electronicsteps is a provider of Suprema and NITGEN fingerprint modules and Quectel GSM/GPRS modules. For more information, contact
[email protected] or
[email protected].
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