According to a recent patent, Apple is improving its fingerprint scanning technology, apparently aiming to bring back Touch ID to iPhone.
The patent, first spotted by Patently Apple and filed with the United States Patent and Trademark Office, is titled “Under-Display Fingerprint Detection Based on Angular Off-Axis Light” and explains how an fingerprint scanner can be made more accurate and reliable.
See also: Is the fingerprint scanner returning to the smartphone screen?
Apple describes its technology as an “enhanced under-display fingerprint sensing” system, which unlike many other fingerprint scanners used in Android, uses “off-axis angular light” to read fingerprints more efficiently without increasing its size.
Most optical under-display fingerprint scanning systems use light emitted from the device's display to illuminate the user's fingertip, which is reflected by the fingerprint behind tiny gaps between the display pixels. A sensor under the display can then read the fingerprint and authenticate the user.
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Due to the “low light output” sometimes caused by the screen itself, the fingerprint image may exhibit low contrast and low signal-to-noise ratio, making it more difficult to read the fingerprint and potentially increasing the time required to verify the user’s identity.
To overcome this problem, Apple proposes a system in which off-axis angular light is captured through a series of “filtering options that depend on the angle between the display and the sensor.” This method can “improve the contrast of fingerprint impressions and keep the entire detection system compact.”
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Specifically, Apple's system includes "a light-emitting layer covered by a transparent layer and configured to illuminate a surface touching the transparent layer and allow reflected light rays to be transmitted from the surface to underlying layers." An optical coupling layer beneath the display "bends the reflected light rays" which are then received by an emulator and interpreted by a pixelated image sensor.
Apple has long been rumored to be bringing Touch ID back under the display on the iPhone, so the patent could indicate that development of the technology is moving forward. There are even claims that the first model to feature the new Touch ID could be the iPhone 13, which is set to be released this year.
