Seeing Beyond Reality: What Are the Key Requirements That Define AR Smart Glasses' Success?

March 18, 2024

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Augmented reality (AR) is nearly here – and when Apple launches a flagship product, Vision Pro, into a market, you know it’s time to take it seriously.

Virtual and augmented reality (VR/AR) technologies have established themselves in gaming and industrial applications but have been slower to break through in consumer. AR glasses have been around for years, but right now there is more activity in this market than ever before, with news about new developments almost daily. The technology has caught up with the product designers’ visions, and big names like Apple, Samsung, and Meta are all announcing products, as well as a plethora of start-ups and smaller players.

Smart glasses for AR may be on the brink of mass consumer adoption.

Different companies are taking their own views on what may be the big use cases – such as Meta talking about AR glasses replacing smartphones by the end of the decade, and Snap looking at AR tourism. (*Source: https://www.theverge.com/2023/2/28/23619730/meta-vr-oculus-ar-glasses-smartwatch-plans) There are also some fascinating products coming from the automotive sector: for example, BMW has announced its ConnectedRide smartglasses, showing navigation and GPS data, while Audi’s activesphere concept car includes Magic Leap’s AR technology.

When AR glasses do break through into the mass consumer market, what will be the technologies that make this happen? What components and subsystems are needed to create AR glasses that consumers will find appealing?

In this article, we review the different subsystems needed, and how they can be combined in a system that is reliable, easy to manufacture, and suitable for mass production.

The Challenges of AR

In AR, a layer of digital text and images is overlaid on the visible real world. This is different from virtual reality (VR), where the user’s view of the world is completely replaced with an artificial image.

To meet consumer expectations of ‘always on’ AR glasses, the display system needs to be lightweight, comfortable to wear all day, and unobtrusive enough so that other people around the user will accept it. Aesthetics are important, and users need to be able to make eye contact with people they interact with.

The most natural choice is to create a pair of smart glasses, that incorporate the display system, electronics and battery into their frame and lenses. This means that there is a need for smart glasses components that are ultra-compact and lightweight.

Previous attempts to create smart glasses have tended to be bulky, heavy products that were uncomfortable to wear. They typically provided low quality visuals, and struggled to create images that were bright enough to see outdoors in direct sunlight. The time between battery charges was short, making them inconvenient for consumers to use in their everyday lives.

To fix these problems, smart glasses need excellent power efficiency, low latency and a clear, bright display – all the while keeping weight as small as possible.

Meeting Expectations for Consumer AR Glasses

AR guru Bernard Kress (Google AR director, and President of SPIE) identifies four criteria as key to mass adoption of AR glasses: wearable comfort, visual comfort, social comfort, and mass production[1]. The glasses must feel comfortable, provide an excellent display, and be acceptable to other people around the wearer – and they must be cost-effective to manufacture in volume.

What makes up a pair of smart glasses?

Figure 1: smart glasses components (All rights reserved by AAC and TriLite)

Depending on the use case, the AR glasses require a microprocessor (the brain of smart glasses) to run everything and deliver a smooth user experience, wireless connectivity such as Bluetooth or Wi-Fi to access information, communicate and interact with apps, and control electronics to drive the light engine (which creates the display), and ensure optimal power management. Depending on the target applications, smart glasses may well also include motion sensors, microphones, loudspeakers, and one or more cameras.

The projection display is the most visible component in smart glasses, if you’ll pardon the pun. This light engine also needs an optical combiner, like a waveguide, to route the light to the wearer’s eye. There are a number of technologies that may be used in the light engine, and choosing the right option depends on comparing their pros and cons, such as cost, weight, image quality, and efficiency.

A critical component of smart glasses is their ability to project high-resolution images onto transparent displays, so the wearer can see the real world beyond the projected image. Achieving this goal requires overcoming several challenges, including balancing image clarity with transparency and creating lightweight displays that don’t obstruct the user’s vision. 

Another factor that is affected by the display system is whether the smart glasses require any kind of fitting process for the user. This is likely to be a barrier to adoption, adding cost and delay to the purchase interaction. To avoid this, the key is to have a display system with a large enough ‘eye box’, which means the glasses do not need to be perfectly positioned in relation to the wearer’s eyes.

Overall, as we mentioned earlier, smart glasses need to be small and light, with excellent power efficiency, low latency, and a clear, bright display.

To address this, TriLite has developed Trixel® 3, the world’s smallest laser beam scanning (LBS) projector for AR consumer smart glasses, using cutting-edge display technology. This award-winning display offers unprecedented size, weight, and image quality.

Software is an essential part of the system. TriLite has taken a ‘software-defined display’ approach, shifting complexity away from hardware, and using proprietary algorithms to ensure optimum image quality, to reduce latency, and to cut power consumption.

Keeping Weight and Size As Amall As Possible

If AR glasses are to be widely adopted, one key factor is their weight. How light is light enough? Glasses that are too heavy will be uncomfortable – and if you’re going to wear them 16 hours a day or more, that’s no good.

Typical glasses today weigh something like 25g to 30g, so AR glasses need to be near that for consumers to accept them. Remember this is for the entire pair of glasses, including lenses, battery, electronics, and the optics system.

How to achieve this? One critical factor is the weight of the battery. All-day battery life is becoming expected for consumer devices, with smartwatches and phones typically achieving 18 hours or more between charges.

To keep battery size and weight low, without degrading the time between charges or the image brightness, you need ultra-low power consumption. Trixel® 3 achieves this with an efficient optical design, resulting in power consumption of less than 320mW (for a typical AR use case with 20% pixel-on at 5 lm brightness).

The optics system is also an important factor in achieving a compact, light design, of course. Trixel® 3 weighs less than 1.5 g and has a volume of 1 cm3. Further space savings are achieved because it does not require any external projection optics or relay optics to couple to a waveguide.

A Clear, Bright Display

There are different technologies that may be used for AR glasses’ displays. These split into two main types: scanning-based displays, such as Trixel® 3’s laser beam scanner (LBS), and panel-based displays, which are like a tiny version of your computer screen.

Choosing the best option for a display requires evaluating the trade-off for parameters like brightness, size, and power consumption. Panel-based displays have been widely adopted, but require external optics, and are bulky.

What about smart glasses using microLED (mLED) displays? For large displays with a large pixel pitch, such as TVs or automotive displays, mLEDS are a viable solution. But for AR glasses, mLEDs with small pixel pitches still need to overcome some fundamental issues for high volume adoption. Firstly, they have lower efficiency for small pixels, which means lower brightness, increased power consumption, and more thermal issues. Small mLED displays also suffer from poor yield, and difficulties in achieving colour and brightness uniformity.

In fact, a scanning display using an LBS is seen by many companies, not just TriLite, as the best option. Figure 2 is from ams OSRAM, TriLite’s partner and supplier of laser diodes for Trixel® 3. It shows how LBS systems scale well to provide a larger field of view, if desired, without increasing the size of the display optics.

Figure 2: comparing display technologies[2]

Bringing It All Together

All of the points we have discussed are important. But they count for nothing if we cannot successfully manufacture smart glasses in volume.

To address the challenges of mass production, TriLite has created an ecosystem of partners and suppliers that are mass production ready. This includes RGB laser diodes from ams OSRAM, MEMS mirrors from Infineon and TDK, and waveguides from Dispelix.

Overall, TriLite has taken a system-based design approach, taking into account all relevant factors – to ensure that smart glasses based around Trixel® 3 can be ultra-compact, ultra-lightweight, and uncompromising in battery life and image quality.

AR glasses may well be about to change the consumer world – and TriLite’s display technology is one of the key pillars to make this happen.