Fingerprint Cards has received a US patent for an optical biometric sensor with tilted mirrors integrated into an active part of a screen.
The design obtains more biometric information from fingerprints in the form of greater resolution using a display that has a protective glass or clear epoxy coating. This layer is a common feature on portable devices like phones and watches, but also on access control systems.
Most of these devices are equipped with capacitive biometric sensors, which have been adapted for most identification tasks to date. The problem is that capacitive sensors require close proximity to the surface of a fingerprint in order to register peaks and spirals with the greater fidelity that is increasingly required.
Even the thin layer of protection used on electronic devices reduces the effectiveness of a capacitive sensor.
Patent fingerprint cards circumvents the problem of excessive depth between a fingerprint and the sensor by reducing this distance using mirrors.
Light illuminating a fingerprint bounces off the surface of the skin through apertures to two sets of extremely small angled mirrors. In some configurations of the patented device, the LCD backlight is sufficient to provide illumination. A secondary source, however, is also disclosed in the patent.
Apertures can be set among LCD components, but in at least one option the apertures float more or less freely. In this case, the biometric sensors are placed among the LCD components.
The first mirrors reflect the light rays at a 90 degree angle through the layer in which the sensors are placed on the second set of mirrors, which return the rays at a 90 degree angle to the sensors.
This design gives a sensor a longer focal length without having to increase the distance between the sensor and the subject – the fingerprint.
New patents for extracting fingerprint features and subject positioning
Two other biometric patent applications from Fingerprint Cards, for ‘single function fingerprint recognition‘ And one ‘authentication method for an electronic device‘, were also published by the USPTO.
The former is an attempt to match features beyond minutiae for less complex fingerprint matching algorithms, while the latter describes a system for using finger position as a means of improving protection against biometric spoofing attacks.
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