- Capacitive fingerprint sensing is the technology used in the world’s best-selling smartphones, in which its ultra-small size – a sensing pad just a few tens of microns thick and a small controller IC – and low power usage are extremely attractive. In a small number of cases, capacitive fingerprint sensing might fail because of ‘dry finger’ problems, or when the user has severe scarring or calluses.
- Optical fingerprint sensing is familiar to travellers who have crossed the US border, where an image of a fingerprint is captured and linked to passport information. An optical sensor is highly reliable and accurate, but the sensors require a backlight to illuminate the finger, and are still comparatively bulky compared to capacitive solutions.
- Ultrasonic sensing offers reliable detection of fingerprints in 3D, but has not found its way into mainstream mobile devices. It is today an expensive and relatively unproven option.
The benefits of capacitive fingerprint sensing that appeal to smartphone makers appeal equally to the car industry. In particular, the ultra-thin sensing pad gives car designers the total freedom they want to design the styling, shape and configuration of the sensor unit to suit the form and functions of the cabin.
Prototypes and demonstrations developed by Synaptics show how a fingerprint sensor may be integrated smoothly into the normal design of a car’s interior without requiring additional surface space, and without cluttering the design of the cabin. Fingerprint sensors may readily be integrated, for example, into a touch-sensing directional pad mounted on the steering wheel (see Figure 2).
This space-saving design allows the fingerprint sensor to be used with both the driver’s hands