Optical Fingerprint News

Imec: Holst Centre, an innovation initiative of imec and TNO, has developed a large-area optical fingerprint sensor that is over 70% transparent for integrating on top of LCD displays. At 70% transparency in the visible region, the new prototype is said to be the most transparent large-area optical fingerprint sensor yet. It is based on a combination of organic photodiodes (OPD), thin-film barrier and oxide thin-film transistors (TFTs) pioneered by Holst Centre. To achieve the high transparency, the team uses photolithography to pattern the photodiode layer within each pixel, creating microscopic islands of photosensitive material.

The transparent sensor offers high resolution and dynamic range with a low dark current, ensuring excellent sensitivity even in low light conditions. It can also be produced in large sizes for example to read palmprints or 4 fingerprints at once. This combination of size and performance enables compliance with FAP 60, the FBI’s most-stringent certification category.

It also allows the sensor to work as a document scanner, for example allowing a single system to read passports and fingerprints while also providing user guidance. Moreover, the new sensor can be used in combination with the highly transparent capacitive touch panels commonly used in LCD screens, enabling simultaneous touch and biometric functionality.

“Integrating biometric sensors into displays allows the display to give people better guidance on how to use the system and exactly where to put their hand. This would make identification, for example at customs, more reliable and much faster. Our patterned pixel design ensures high transparency and is completely compatible with existing flat-panel display production processes, making integration with widely used LCD displays both technically feasible and cost effective,” said Hylke Akkerman, Program Manager at Holst Centre.

As with Holst Centre’s previous fingerprint sensors, the transparent sensor is also capable of detecting a heartbeat while reading a fingerprint for liveness detection. Changes to the photodiode chemistry would allow the sensor to work in the NIR to detect the pattern of veins in the hand, offering additional ways to verify a person’s identity.

Holst Centre will also be showing three further fingerprint innovations including a high-resolution sensor integrated under a display using Holst Centre’s proprietary collimator technology as well as an in-display sensor concept that uses photolithography patterning to integrate OLED and OPD pixels side-by-side. This latter approach could allow 500 ppi fingerprint scanners to be integrated into ultra-high resolution display arrays such as single AMOLED modules with multiple functionalities. On the design side, Holst Centre will demonstrate integrated readout electronics for on-display-panel fingerprint detection.

“Integrating microscopic photodetectors within AMOLED arrays adds light sensitivity to display pixels. Through photolithography patterning, we envision ultra-high resolution arrays of OLEDs and OPD that maximize the usage of the active area. At the same time, in-panel readout blocks could facilitate further scaling of fingerprint scanners for a more-efficient user interface,” adds Pawel Malinowski, Program Manager at imec.

PRNewswire: AU Optronics (AUO) unveils what it calls the world' first full screen optical in-cell fingerprint LTPS LCD, in-cell touch LTPS LCDs with the world's smallest through-hole design and narrowest(*)1.0 mm bottom border for smartphone applications. AUO's 6-inch full screen optical in-cell fingerprint LTPS LCD is the first of its kind to have installed an optical sensor within the LCD structure. Equipped with AHVA technology, full HD+ (1080 x 2160) resolution and 403 PPI pixel density, the panel has a full screen sensing area with the same 403 PPI sensor density and 30 ms swift sensor response time for the smoothest and most accurate sensing performance possible on a smartphone.

Also applying the AHVA technology, the 6.3-inch in-cell touch LTPS LCD has full HD+ (1080 x 2304) resolution and possesses the world's narrowest 1.0 mm bottom border, which is around 40% narrower than that of its counterpart in the market.