FingerChip® Technology
The FingerChip is a fingerprint sensor designed and manufactured by Atmel, a global leader for biometric sensors and solutions. It uses a sensing technology based on a thermal principle. The origins of the FingerChip are related to research done around 10 years ago on Infrared cameras.
Technology:
The goal of a sensor is to measure the presence of a fingerprint ridge or valley in order to output an image that can then be processed by authentication software.
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FingerChip’s thermal sensing technology measures the temperature difference according to whether the finger skin touches the sensing area (for a ridge) or not (for a valley) . There is therefore no measure of the exact skin temperature, but rather of the heat (energy) transferred from the skin to the sensor when contact occurs. FingerChip is physically made of a silicon die covered by a pyro-electric material, in other words a material which is sensitive to temperature differences. The die itself is made of a matrix of adjacent pixels.
The temperature difference initially appearing at the pyro-electric layer contact is transformed into electrical charges thanks to the material's properties. Those charges are then amplified and measured by the underlying silicon pixels, in order to create a black & white image (in fact several gray levels), an accurate transcription of the user's fingerprint. |
This thermal technology has many advantages. In particular, it provides a high quality image even on poor fingerprints such as ones that are dry or worn, with little depth between the peaks and the valleys of the fingerprint. It also operates well under drastic environmental conditions, such as extreme temperatures (the sensor is qualified between –40°C and +85°C), high humidity, dirt, oil and water contamination. Lastly this technology has an unmatched asset compared to other - especially capacitive – ones: the small dependence of distance between the finger and the sensor allows complete encapsulation and protection of the sensor with a very robust coating, providing a very high resistance to shocks, abrasion, water or any other environmental stress.
Acquisition Process:
The FingerChip is the first sensor to use a sweeping procedure. This process, patented by Atmel in 1996 and 2001, aims at reducing the required size of the silicon to manufacture a fingerprint sensor, in order to reduce the cost and get rid of latent prints naturally present on the surface of area sensors. These latent prints can be re-used without the user knowing it in order to get into the “protected” system. The sweeping methodology is therefore a much more secure process. |
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Its principle consists of acquiring successive slices of the fingerprint, before reconstructing the complete image.
Thanks to the multiple advantages of thermal technology and sweeping procedure, the FingerChip is a perfect fit for today’s consumer applications.
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