A Silicon Valley-based startup has recently emerged from stealth mode to reveal what it claims is the smallest, most pixel-dense dynamic display ever built. Mojo Vision’s display is just 0.48 millimeters across, but it has about 300 times as many pixels per square inch as a typical smartphone display.
The display used microLED technology instead of OLEDs (as in several generations of Samsung devices and the iPhone X) or an LCD (as in every other iPhone). Made from gallium nitride, microLED displays can consume as little as 10 percent of the power of LCDs and are 5 to 10 times as bright as OLEDs. That combination makes them a good fit for head-up displays and other augmented reality applications.
Like other microLED companies looking to power augmented reality devices, Mojo Vision builds it gallium-nitride microLEDs as an array and then bonds the array to a silicon CMOS backplane that switches them on and off. Paul Martin, vice president for displays, says the company had to overcome several hurdles to build the 14,000 pixels-per-inch display. “The pixels are 1.3 [micrometers across], which means that the gap is only 0.5 µm. Smaller gaps creates harder and harder problems of fabrication.” He would not detail how the company overcame this problem and others.
A closeup of Mojo Vision's 14,000-pixels per inch display.Photo: Mojo Vision
MicroLED displays targeted at AR are typically measured in centimeters, not fractions of a millimeter like Mojo Vision’s. “The dimensions of it are purpose built for the application we’re going to use it for,” says Martin. “We need it to be incredibly small in overall dimensions so it is not blocking your real-world view.”
Company executives were cagey about exactly what the final application will be. Mojo Vision, they say, was founded with a particular application in mind. The microLED display “is one piece of several building blocks that we have to have in place to build the product that we’re making,” says Steve Sinclair, senior vice president of product and marketing at Mojo Vision.
The best clues to its purpose are in Mojo Vision’s stated pursuit of something it calls invisible computing—basically information that’s there when you need it and gone when you don’t. It’s proved a compelling enough idea that the company, which is just over 3 years old, has attracted a total of $108 million in venture capital to date, some of it from the venture arms of big tech companies including Alphabet, HP, and LG.
Sinclair and Martin say that the company is not done boosting the pixel density of the display. “Our goal is to match resolution of the human eye eventually,” says Sinclair. He agreed that resolution depends on how close to the eye the display is, but said that talking about what that distance is is not something they would do yet. “Devices are becoming more personal. As they become more personal they get closer to eye, and they need more pixels,” says Sinclair. “We’re trying to build something personal that is always with you but is small enough so it doesn’t distract you.”
This post was corrected on 3 June 2019 to give the proper inter-pixel spacing.
Samuel K. Moore is the senior editor at IEEE Spectrum in charge of semiconductors coverage. An IEEE member, he has a bachelor's degree in biomedical engineering from Brown University and a master's degree in journalism from New York University.