Large-area under-display biometric fingerprint sensing shown in Apple patent application
The patent published by the World Intellectual Property Organization (WIPO) describes the use of a narrow field-of-view collimator and a thin-film transistor (TFT)-based organic imager. A collimator is a device for focussing or narrowing waves, such as of light, and serves the purpose of separate weak reflection generated by angled illumination of the walls of fingerprint valleys. Collimating the reflected lights enables a one-to-one imaging ratio between the finger surface touching the transparent layer and the sensor, Patently Apple explains.
The advantage of the proposed system is the capture of fingerprint biometrics within a significantly larger surface area, though Apple notes that the glass-air interfaces of mobile devices are not stable enough to support small area matching, while CMOS large-area sensors are not cost-effective. Separating the different reflected rays at various angles could also be a challenge, with a large number of illumination patterns necessary, which can extend image capture times to a few seconds, according to the report.
A touch-display layer, a collimator layer, and a pixelated image sensor make up the system. The touch layer could be a glass-covered OLED screen, and the collimator layer may be a fiber-optic plate constructed with an opaque separator material.
The patent application was filed in July of 2019, and the timing of any potential implementation of the technology is currently unknown.
Apple recently resurrected Touch ID for the new iPhone SE, and an accumulation of related patents has raised speculation that the iPhone 12 will include the first-ever under-display Touch ID, though leaked images do not indicate the feature will be included.