Two showroom visitors, ten minutes apart, tried on different display glasses and asked me almost the same question: "Isn't this the same trick, just a different brand?" It isn't. The Even G2 and a birdbath-style device such as those from Rokid or XREAL both put a digital image in front of your eye, but they get there with two genuinely different optical tricks — and you notice the difference the moment you put either one on.
Short answer: a waveguide (used in the Even G2) steers light through an almost invisible structure etched into the lens itself, so the glasses look like ordinary clear eyewear and you see a small, bright text overlay floating in part of your field of view. A birdbath-style virtual monitor bounces the image from a tiny microdisplay off a curved half-mirror into your eye, which needs more room and a tinted, thicker combiner lens — in exchange you get a larger, screen-like image. In short: waveguide stays discreet and wearable all day; birdbath trades that discretion for a bigger picture.
Two very different ways to put an image in front of your eye
"Display glasses" sounds like a single technology. It isn't. Under the hood there are several genuinely different approaches to the same basic problem: how do you get a digital image close enough to the eye to look sharp and comfortable? Waveguide and birdbath are the two you're most likely to run into.
In a waveguide, the approach Even uses in the G2, a tiny projector module in the temple creates an image that travels through microscopic structures etched into the lens itself — not unlike light travelling down an optical fibre until it exits at a specific point in front of the eye. The lens stays thin and clear, because the structure only needs to redirect light, not house a large curved mirror in the light path.
In a birdbath setup, used by makers of XR glasses built around a large virtual screen (see our comparison against Rokid), a small microdisplay usually sits above or beside the lens. Its image bounces off a curved, semi-transparent mirror back into the eye — hence the name, the optical path resembles a small birdbath. That mirror and the beamsplitter it needs take up volume, and the front lens is usually tinted so the reflected image doesn't wash out in ambient light.
What you actually see with a waveguide like the G2
Put on the G2 and the first thing you notice is: glasses. The lenses are clear, untinted, and look like an ordinary pair of prescription glasses at a glance. Turn on a display — a notification, the teleprompter, a translation line — and a compact, monochrome (green) text overlay appears in a limited part of your field of view, while the rest of what's in front of you stays visible and unchanged. It feels less like "a screen in front of your eye" and more like a small, bright note hovering somewhere in your upper field of vision. For text — a name, a cue, a line of translation — that's plenty; it isn't built or intended for video, photos, or a full-screen experience.
We're deliberately not quoting degree or nit figures for exactly how "big" or "bright" that field is — we don't have independently verified numbers we'd stand behind, and inventing some would only hand you false precision. What matters is the character of it: small, discreet, text-first, inside glasses that otherwise look completely normal.
What you actually see with a birdbath-style virtual monitor
Put on a birdbath device instead and the first difference is visible before you even switch anything on: the front lenses are noticeably darker and the frame is thicker at the front, because the mirror, beamsplitter and microdisplay all need somewhere to sit. Switch the image on and — unlike the waveguide — you see a larger, self-contained image that reads more like a floating screen: suited to a video, a presentation, several windows side by side. In exchange, the world around you comes through dimmer through the tinted lens, and as everyday eyewear — across a table in conversation, walking down the street — it's more conspicuous and bulkier than a clear waveguide model.
Again, we're not inventing field-of-view or brightness numbers for birdbath devices; makers such as XREAL or Rokid publish their own figures, and we won't repeat them here unverified. The honest, optical core of the difference is: more screen, more bulk, more tint.
Waveguide (Even G2)
Clear, thin lenses that look like ordinary glasses. A small, bright text overlay rather than a full-screen image. Built for notes, translation, the teleprompter and notifications — wearable all day, barely recognisable as tech.
Birdbath (e.g. Rokid, XREAL)
Darker, thicker front lenses with a visible mirror assembly. A larger, self-contained image for video, presentations, a screen-like experience. Built more for a dedicated session at a desk or on the move with a source device than for wearing all day in conversation.
The honest limits on both sides
Neither approach is simply "better" — they optimise for different things, and both pay a price for it. The waveguide wins on discretion and all-day wearability but gives up screen size: it's built for short, text-based information, not a movie-watching experience. The birdbath setup wins on screen size and immersion but gives up subtlety, weight, and often all-day comfort — and the tinted optics change how other people perceive you and your surroundings through the lenses.
One point that often gets lost in a sales pitch: waveguide glasses like the G2 are built for people who want to wear glasses almost continuously — in meetings, while travelling, in conversation. Birdbath devices are mostly built for a deliberate session where you consciously step "into a screen." Mix up those two use-cases and disappointment follows, regardless of brand.
Buy, skip, or test first?
A waveguide model like the G2 fits if you want glasses that look and feel like glasses all day, discreetly showing you text — notes, translation, cues — without the person across the table noticing.
A birdbath model fits better if your main need is a large, private screen for video, working across several virtual windows, or gaming on the move, and you're willing to accept darker, thicker, more noticeable glasses in exchange.
Test both yourself before deciding — ideally side by side, because no description, including this one, replaces the moment you actually look through both lenses. You'll find a direct comparison of the G2 against a birdbath device in our Even G2 vs Rokid comparison; to see every model and optical type side by side, check the AI glasses database or our general comparison guide.
Disclosure: AI-Eyewear is the authorised Swiss reseller of Even Realities. We describe birdbath devices fairly as their own category built for a different purpose — not as an inferior copy of the G2.