Augmented reality (AR’s) Technology Roadmap
Mark Zuckerberg called AR glasses “one of the hardest technical challenges of the decade.” Due to the complexity of the architecture, the price of AR glass is still high, which hinders penetration. For example, one of the products from a leading industry player sells for US$3,500 and the majority of the users are enterprises. Unlike VR, in which most components are becoming mainstream specs, AR makers are still exploring different architectures:
Display: DLP, LCOS, Si-OLED are mainstream and MicroLED would likely be the ultimate solution
AR glasses require compact and power-efficient displays with very high contrast and brightness. We had a leap in AR display technology achieving these objectives, yet there is still room to improve on the yield rate and costs. Organic light emitting diodes on silicon (OLEDoS), digital light processing (DLP), and liquid crystal on silicon (LCOS) are the three main pathways:
(1) OLEDoS is fabricated on silicon wafers instead of glass substrates and polyimide substrates.
(2) DLP is a popular solution for projectors, using micro mirrors (DMDs) which are positioned in a semiconductor chip to reflect light, and directs red, green, blue light to the imagers.
(3) LCOS technology is a variation of LCD technology, separating light into red, green and blue components and reflecting the light off the chip surface to LCD cells. A CMOS chip is under the chip surface to control voltage on square reflective aluminium electrodes.
Initially, LCOS was the major technology for AR, for the high brightness, but it was not energy- or cost-efficient. OLED has limitations with brightness; however, breakthroughs in OLED material such as silicon substrate bridged the gap.
Therefore OLEDoS (OLED on silicon) is now becoming the most popular technology due to its merits of higher contrast, power efficiency, thickness, wider temperature range, and faster response time. Although there are still many hurdles to achieving mass production, we believe micro-LED would be the ultimate solution for AR glasses due to its super-high brightness and contrast, excellent temperature endurance, fast response time, and low energy consumption.
Optics: Waveguide becomes the major architecture
The industry is developing two different approaches in waveguide technology:
(1) Diffractive waveguides are considered the most mature technology, used in HoloLens 2, Magic Leap 1 and Vuzix M4000. A diffractive optical element (DOE) or holographic optical element (HOE) are used to inject the light over a small area into the waveguide and extract it to the user’s eyes. The diffractive method disperses wavelengths, so separate waveguides are used. Mainstream products are leaning towards the use of two layers of waveguides for thinner glasses.
(2) Reflective waveguide designed by the Israeli AR company, Lumus, does not require nano photonics. This methods employs a 1D or 2D semitransparent mirror along the optical path to guide the light to users’ eyes.