Tiny Lasers Could Finally Bring Us Really Smart AR Glasses Post– Google Glass, a new alliance says it has the winning tech
BY KATHY PRETZ |27 AUG 2021 |5 MIN READ
When Google Glass debuted almost a decade ago, augmented reality (AR) wearables seemed poised to take off. Smart glasses let users surf the Internet; access maps, calendars, and other apps; and even call up recipes. Users could simultaneously interact with the physical and digital worlds.
But Google withdrew its smart glasses from the market in early 2015. Several reasons have been given for their demise, including poor marketing, an unattractive design, too many software glitches, and a short battery life.
"The technology Google Glass needed [to succeed]—such as illumination sources, compact projectors and optics, and a whole host of other things—was not mature enough at that time to meet all the requirements of design, performance, and use," says Bharath Rajagopalan, director of strategic marketing for STMicroelectronics, a multinational semiconductor manufacturer and a leader in microelectromechanical system (MEMS) technologies. "Sometimes when you're too early to the market, you don't have all the necessary elements."
Since the demise of Google Glass, companies have attempted to improve the design, performance, and functionality of smart glasses. The newer products include Blade glasses by Vuzix and Focals by North, which Google acquired last year.
Meanwhile, glasses with audio features only, including Bose Frames and Amazon Echo Frames, have sprung up. Facebook recently announced a collaboration with Luxottica on its version of audio-only smart glasses.
Some of the major players in the field say that for smart glasses to become more popular, they must be lightweight, low-power devices that are fashionable. A key enabling technology, they say, is laser-beam scanning (LBS) solutions, which ST has been a pioneer in developing.
LBS is gaining adoption for use in smart glasses because it uses a compact projector, produces a bright image with rich colors, consumes relatively little power, and can be integrated aesthetically into a pair of glasses, Rajagopalan says. Tiny MEMS mirrors create images by deflecting the laser beams emitted from compact diodes. They project the images onto waveguides or other combiner optics, he says. The combiner optics are typically embedded in smart-glasses lenses, onto which the images are projected, Rajagopalan says. Focals by North glasses use LBS technology.
Rajagopalan says the micromirrors and other tiny components—including lasers, projectors, and batteries—can all be housed unobtrusively in a module small enough to fit inside the frames.
What's unique about laser-beam scanning is it really fits the bill on size, weight, power, performance, and image fidelity.
To advance the technology, ST launched the IEEE Laser Scanning for Augmented Reality Alliance in March. Rajagopalan is the LaSAR Alliance's chair. Other members include Applied Materials, Corning, Dispelix, Inkron, Mega1, and Osram. The companies share information about laser-scanning technology and collaborate on the development of components, devices, and techniques.
LaSAR is the newest program of the IEEE Industry Standards and Technology Organization (IEEE-ISTO), which provides its customers with legal and financial infrastructure and administrative support for standards development and market adoption of emerging technologies.
Rajagopalan says an added benefit of forming LaSAR under IEEE-ISTO is that many of the representatives from the member companies are IEEE members.
"LaSAR's association with the world's largest and most prestigious and credible professional technical organization is something that we find very attractive," he says.
Being exposed to numerous technologies and IEEE's societies is an advantage, he adds, as is the potential for collaboration.
SMARTER GLASSES
AR smart glasses should look, feel, and perform like real eyeglasses—with the additional benefits of augmented information, Rajagopalan says. That means they should be able to be worn all day, have lenses that can automatically darken when exposed to sunlight, and weigh about the same as a pair of traditional eyeglasses: 70 grams or less.
Smart glasses can be useful for AR as well as mixed reality (MR) and even extended reality (XR) applications, he says.
MR, an extension of augmented reality, combines physical and digital content so that the physical and digital images become indistinguishable. Microsoft's HoloLens is an example.
XR merges VR, AR, and MR and immerses the user in a virtual environment, ideally augmenting the user's surroundings.
LaSAR is considering a range of factors that impact usability and convenience. That includes the "eyebox" size, field of view, range of resolution, latency, and power consumption, Rajagopalan says.
The eyebox, an important consideration in the design of optical systems, is best understood in the context of binoculars, Rajagopalan says. Viewers adjust binoculars to fit the eyepieces to the distance between their pupils. A similar effect happens in AR smart glasses. To account for variations in the distance between the pupils and avoid vignetting images, smart glasses need an eyebox greater than 10 millimeters by 10mm—which can accommodate most people, Rajagopalan says.
The field of view is the extent within which the virtual images are displayed. For smart-glasses applications, a FoV in the 30-degree to 40-degree range generally is good enough. For more immersive applications, such as MR, a much higher FoV—typically more than 80 degrees—is more appropriate. Smart glasses can accept a smaller FoV because only information related to the user's direct FoV is useful. For MR, on the other hand, placing photorealistic virtual objects in the physical world and having a wide FoV allows the user to move his or her head around to interact with virtual objects, Rajagopalan says.
As with most engineering challenges, there are trade-offs to consider, he says. One example is the FoV-to-eyebox coupling (known as the Lagrange invariant). Improving one variable significantly impairs the other. There are also trade-offs among FoV, resolution, and power. But Rajagopalan says LBS offers scalable solutions that allow developers options to optimize settings for their applications.
"What's unique about laser-beam scanning is it really fits the bill on size, weight, power, performance, and image fidelity," Rajagopalan says.
COMPACT SYSTEM
As a proof of concept, ST built a laser-scanning system for AR smart glasses. The projector consists of two key parts: an optical engine and an electronics module. The optical module is approximately 0.7 cubic centimeters and contains the micromirrors, laser diode, combining optics, photodiode, and thermal sensor. The electronics module contains the MEMS mirror driver, digital controller (for video processing and closed-loop control of the projection system), laser diode drivers, and other electronics.
The prototype consumes less than 1 watt of power. Still, ST is refining techniques to cut energy usage by more than 50 percent through the development of next-generation MEMS mirrors using piezoelectric technology and drivers as well as advanced laser diode drivers, Rajagopalan says.
ST has demonstrated the prototype's suitability at industry and trade events, he says. The prototype enables the development of reference designs that manufacturers of AR smart glasses and related products can use for product development, he says. ST is working with Quanta Computer to speed up its efforts.
COMMON APPROACHES NEEDED
The formation of the LaSAR Alliance was largely driven by the need for an ecosystem and supply chain, Rajagopalan says.
Alliance members contribute different elements of the supply chain, he says. ST, for example, makes the MEMS micromirrors and the drivers for the mirrors and laser diodes, plus their chipsets. Osram develops laser diodes. Dispelix designs the waveguides. MegaOne builds projectors.
The alliance welcomes new contributors, Rajagopalan says. (To become a member, fill out this form.)
One of the challenges alliance members are working through now is a standard way to measure image quality, Rajagopalan says.
"Because AR smart glasses are still such a nascent market," he says, "there has not been any common approaches to building systems or even a common language. Everybody has been doing their own thing—and we're progressing to fix that."
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資料來源: https://spectrum.ieee.org/tiny-lasers-could-finally-bring-us-really-smart-ar-glasses
