Can microLEDs help displays better sense the world?

An article written by Eric Virey, principal display market and technologies analyst in the Photonics, Sensing & Display division at Yole Intelligence part of Yole Group, for Information Display – Among the benefits of microLED displays, the possibility of integrating a variety of sensors directly on the front plane is probably the most intriguing and exciting.

Smartphones, laptops, and other electronic devices have become integral parts of our lives. From leisure to staying connected with friends and family or managing work on the go, these devices have transformed the way we live and work. Display technology is critical. For mobile devices, the ability to interact directly with content via touchscreens has revolutionized human-machine interaction. But this is just the beginning. Over the last few years, devices have evolved to include more sensors that enhance the user’s experience and security. These include proximity sensors, fingerprint readers, 3D sensing for face identification, iris scanning, and front cameras.

The multiplication of sensors, however, is at odds with other desirable attributes: aesthetics and functionality also are driving the need for the highest possible screen-to-body ratio (i.e., the elimination of the bezel and cut-outs in the displays). Initially positioned outside the display (on the edges of the devices), sensors have progressively been embedded in the display real estate because of progress in technologies for display cut-outs and punch-holes.

Yole Intelligence asserts that ideally, sensors would become totally invisible and disappear under the display. This, however, poses enormous challenges, because sensors need to collect information (such as light and sound) from the device’s environment. Many also need to send a signal to the outside world and collect data about how the environment altered this signal. The display then constitutes a formidable obstacle to these two-way exchanges between the sensor and the environment.

An “under-display” sensor must receive the signal in and out through the display and still be thin enough not to increase the device’s thickness. This implies specific designs not only for the sensor, but also, in most cases, for the display so that the signal can travel through it both ways and remain exploitable.

The Transition to Under-Display Features

The first sensor to move behind the display was a fingerprint scanner (FPS). Reliable authentication has become a critical feature now that we are entrusting our mobile devices with a flurry of personal and critical information, such as banking credentials and health-related data. Traditional capacitive FPS requires that the distance between the finger and sensor remains quite short and, therefore, is not suitable for under-display integration. However, in 2017, Qualcomm developed a 440-µm-thick ultrasonic FPS that could operate under 0.8 mm of glass…

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