Under-the-display sensors

CEA-Leti has developed a new optical sending architecture that combines a microLED and an organic photodetector (OPD). This system-level approach,  that combines device design, electronics, and modeling allows for multifunctional display applications, without compromising display performance.

The researchers have optimized both devices to a green wavelength, that is relevant to photoplethysmography (PPG) signal extraction.

Researchers from France's CEA Leti have reported on the successful integration of organic photodetectors within microLED displays, to create a multifunctional display, that can combine imaging with gesture recognition, and even biometric scanning.

As microLEDs are extremely bright, it is possible to create displays with very high aperture ratio (compared to other displays such as LCDs and OLEDs) which frees up space on the display panel. 

This is a guest article by Dr. Reza Chaji, founder and CEO, VueReal

Imagine a future where your smartwatch evolves from a timepiece to a powerful digital hub, seamlessly integrating all aspects of your life. The potential for smartwatches to become central to daily routines is immense, especially with AI and cutting-edge technologies.

These advanced technologies enable smartwatches to support seamless communication, health and fitness tracking, environmental awareness, biometric security, and more. As a result, smartwatches are becoming indispensable tools that enrich our lives and enhance our health and security in an interconnected world.

AUO had an impressive booth at Displayweek, showing some of its latest microLED prototypes. It is clear that the company is highly focused on microLED technology as its next-gen display strategy.

First up, with a 31" large area single-panel microLED, which AUO says is the world's largest. The display is produced on a single glass LTPS backplane, and offers 120Hz and a brightness of 500 nits. AUO calls this a Large Size A.R.T. MicroLED display.

Taiwan's leading research institute, ITRI, developed a new in-cell technology to integrate sensors within microLED display panels.

ITRI says that it is the first in the world to enable a full-screen multi-finger fingerprint sensor. ITRI says that its new technology does not increase the display's thickness and can thus be implemented even in small wearable smartwatch displays.

This is a guest article by IdeaFarm LLC

A potentially key advantage for microLED displays is the ability to effectively integrate far-field image sensing within the display because of the large “open” pixel area compared to other display technologies. The basic feasibility and advantages of integrating far-field image capture within a microLED display was reported on by IdeaFarm LLC at the recent Displayweek 2021 conference (the major worldwide display technology conference). IdeaFarm proposes to integrate an array of miniature wafer-based camera chips, “microcameras”, on the same substrate as microLEDs as part of the display manufacturing process (see diagram below for an illustration of the concept). Advanced real-time image processing is used to form high-resolution video by combining lower resolution video streams from multiple microcameras.

Because of the recent increased attention to improving the videoconferencing experience and the ongoing drive to eliminate bezels and display cut-outs in mobile phones and other devices, interest in including image capture inside displays is growing rapidly. The number of technical papers presented at Displayweek related to including image capture inside the display grew from essentially zero in 2019 to eleven in 2021. So far, under-screen or under-display cameras have been demonstrated in mobile phones with OLED displays, but only one brand is actually shipping and the tradeoffs in image quality and visibility of the camera zone have been noted.

Digitimes posted an interesting research note, in which they state that micro-LED displays may find it hard to compete with LCD and OLED displays as the market is approaching saturation.

Micro-LEDs have several advantages over other displays - high brightness, quick response time and the ability to create flexible and transparent displays (this is also true for OLEDs). However a major advantage for Micro LEDs is that the aperture ratio is only 10%, which means that there is a lot of empty space in a micro-LED display.