The company showed a 14.3-inch Panoramic Head-up Display (PHUD) using microLED technology. It offered a resolution of 1700 x 650 with luminance of 100K/130K (Typ./Max) with a 120 Hz refresh rate. Like the Tianma HUD, the display reflects directly off the windshield, so it offers no real virtual distance.

TCL-CSOT also showed an AR-HUD demo using a 4.6-inch microLED panel in a cockpit demonstrator. This offers a resolution of 1280 x 720 with 140K nits out of the PGU and 18K nits to the eye.

In paper 61-4, TCL-CSOT explains more about the design of the cockpit version of the microLED panel – the one that offers 18K nits to the eye. The microLED pitch is 80 microns and microLED devices of various sizes can be used (15×25, 15×30 or 25×30 microns). To capture more light form the Lambertian-emitting microLEDs, the company designed a microlens array. The result is a horizontal half angle of about 30° and a vertical half-angle of about 25°. Image distortion is below 2% via an algorithmic approach.

A second AR-HUD stand-alone demo used a similar 4.6-inch microLED panels but noted the luminance was 200K nits with about 25K nits to the eyebox in normal mode and 6K nits in sunglasses mode. We assume the sunglasses are simply acting as a polarizer to filter the s- and p-polarized microLED light, so why isn’t the sunglasses mode closer to 12K nits?

Paper 81-4 described some of the issues behind hidden microLED displays, sometimes called smart surfaces. Here, microLEDs offer a clear value proposition: they can be very bright and very small. For example, if the LEDs are fabricated with a 0.5mm pitch, then 95% of the area can be patterned with a texture and the microLEDs will be invisible when off, but clearly visible when on. In this paper, they examined several ways to pattern the textured ink. They settled on a screen-printing technique with an accuracy of +/- 15 to 25 microns. Transmissivity of the microLEDs is 95%.