Electrochromic dimming

Electrochromic dimming is the use of an electrochromic layer, a thin-film stack whose light transmission changes when a small voltage is applied, to darken or clear the front lenses of AR glasses and other optical see-through displays on demand. An electrochromic material is defined by its ability "to sustain reversible and persistent changes of the optical properties when a voltage is applied to it"; the effect was discovered in tungsten oxide thin films, which Granqvist's 2000 review called the most promising candidate material for electrochromic devices.

In AR hardware the tinted lens cuts the amount of ambient light that reaches the eye, so the projected image keeps its contrast in bright rooms or outdoors and the wearer can switch between a see-through view and a darker, more enclosed viewing mode. Consumer display glasses such as the Xreal Air 2 Pro, Xreal One, Xreal One Pro, Viture One and Viture Beast use electrochromic lenses with a fixed set of tint levels, from two on the Viture One to nine on the Viture Beast. The technique is distinct from photochromic lenses, which darken automatically in response to ultraviolet light rather than an electrical signal, and from liquid crystal dimming films. The Magic Leap 2 enterprise headset uses a dimmer that Magic Leap does not describe as electrochromic.

Reviewed 27 September 2026. Checked every cited source against its claim: Granqvist 2000 and Deb 1973 papers, Sony 2018 SID abstract, Wang 2025 paper, SPIE article, Magic Leap 2 white paper, Road to VR, Guttag, Gentex release, XREAL product pages and the TechRadar, Tom's Hardware, Tom's Guide, Laptop Mag and Gaming Nexus reviews. About review dates.

How it works

Granqvist's review introduces electrochromism in tungsten oxide through the simplified reaction WO₃ + xM⁺ + xe^- ⇌ M_xWO₃, where M⁺ is a small ion such as H⁺, Li⁺, Na⁺ or K⁺. A tungsten oxide film is transparent, but when it takes up electrons and charge-balancing ions it turns absorbing if the material is heavily disordered, or infrared-reflecting if it is sufficiently crystalline. The change is reversible.

A practical device is usually built as a five-layer stack on one substrate or between two. A pure ion conductor sits in the middle, with the electrochromic layer on one side and an ion storage layer (the counter electrode) on the other; two transparent electrical conductors form the outer layers. Applying a voltage between the conductors moves ions back and forth between the electrochromic layer and the counter electrode, and the optical change follows. Granqvist compares the stack to a thin-film battery whose state of charge shows up as an optical effect. Because the device has open-circuit memory, the voltage only needs to be applied while the tint is changing. Material choices change the result: combining cathodically coloring tungsten oxide with anodically coloring nickel oxide gives high coloration efficiency, and one polymer-electrolyte design added molybdenum doping to the tungsten oxide film to make its color more neutral.

The clear state is never perfectly clear. Wang and colleagues note that in electrochromic devices the loss of transmittance in the bleached state comes mainly from the indium tin oxide (ITO) conductor layers, and that the electrolyte also affects the achievable contrast.

History

In a 1973 paper in the Philosophical Magazine, S. K. Deb reported that amorphous tungsten trioxide films developed a broad color-center absorption band, peaking at 9100 Angstrom, both when irradiated with light of wavelengths shorter than 3500 Angstrom and when an electric field of about 10⁴ V/cm was applied; fully oxidized films showed no coloration. Granqvist's review states that the electrochromic phenomenon was discovered in tungsten oxide thin films, and a device design whose outer conductor is a semitransparent gold film is known as a "Deb device".

Granqvist's 2000 review names "smart windows", which vary how much visible light and solar energy passes through, as a key application of tungsten oxide electrochromic films, and also lists devices that modulate reflectance for anti-dazzling rear-view mirrors in cars and trucks, and non-emissive information displays. In October 2007 Gentex, a supplier of automatic-dimming rear-view mirrors, announced that it had shipped the first set of dimmable aircraft window shades to PPG Industries' aerospace products group for the passenger cabin of the Boeing 787 Dreamliner; the electrochromic shades dim to five levels, controlled by a switch next to the window seat. Reviewers later used the same comparison for XR glasses: Laptop Mag described the electrochromic film on the Viture One as the technology behind the buttons that darken aircraft windows.

Work on dimmers made specifically for AR glasses appeared in the display literature by 2018. In a paper in that year's SID Symposium Digest of Technical Papers, a Sony team described an electrochromic dimming device on a plastic substrate that modulated transparency from 70% to 10%, could bend to a radius below 30 mm, survived more than 10,000 cycles and high-temperature, high-humidity conditions, and, combined with AR glasses, kept the virtual image clearly visible "in various environments". By 2023 consumer display glasses with electrochromic lenses were on the market and being reviewed, including the Viture One and the XREAL Air 2 Pro.

Why AR displays need dimming

In an optical see-through display the virtual image is added to the light that already comes through the lens. Paul Cain, strategy director at FlexEnable, which develops liquid crystal dimming films, gives the practical effect: "A virtual object that appears relatively bright and high contrast in an office environment may appear at best semitransparent and washed out in a sunny outdoors setting, preventing the virtual object from occluding anything behind it." Raising display brightness is the other option, but it has limits. Magic Leap wrote in its 2022 optics white paper that although the Magic Leap 2 reaches up to 2,000 nits, this "still isn't enough to compete with direct sunlight", and that making the display brighter would have needed more power and a bigger form factor.

Dimming the whole lens ("global dimming") acts like adjustable sunglasses; Cain lists electrochromic and liquid crystal approaches as the candidate technologies for it. Wang and colleagues describe the same aim in materials terms: electrochromic dimmers are attractive for AR lenses "owing to their ability to control light transmittance", and a high-contrast dimmer could also let one pair of glasses move between transparent AR and opaque VR-style viewing.

Comparison with other dimming methods

Method	Trigger	Typical use in head-worn displays	Notes
Electrochromic layer	Applied voltage	Global dimming in consumer display glasses (XREAL, Viture)	Voltage needed only while switching (open-circuit memory); preset tint levels chosen by the wearer
Guest-host liquid crystal film	Applied voltage	Global dimming	Dyes in a liquid crystal mixture; FlexEnable cites switching of about 10 ms
Pixelated or segmented liquid crystal dimmer	Applied voltage, per region	Local dimming behind virtual content (the Magic Leap 2 dimmer, according to Karl Guttag's reading of Magic Leap patents)	Cain states that the switching speed needed for spatial dimming "necessitates an LC-cell"
Photochromic lens (for example Transitions)	Ultraviolet light	Sun lenses on camera and AI glasses such as Ray-Ban Meta	Darkens automatically outdoors; car windows block UV, which can keep the lenses from darkening fully
Clip-on shade or cover	Manual	Accessory for display glasses	All-or-nothing light blocking

Photochromic and electrochromic behavior can occur in the same material: Granqvist notes that tungsten oxide films also show a photochromic effect under ultraviolet light. On camera-equipped AI glasses, photochromic lenses are offered as sun lenses. EssilorLuxottica describes Transitions lenses on its Meta glasses as shifting "from a light tint indoors to a darker sun lens outdoors", and in March 2026 it offered the Oakley Meta Vanguard with Transitions lenses for the first time.

Magic Leap 2 dimmer

The Magic Leap 2 uses a dimmer that Magic Leap does not describe as electrochromic. The company calls it the first general-purpose AR device "to feature dimmers integrated into the optical stack". Its lens stack includes a reflective polarizer "to polarize the world light" and a dimmer assembly, and the dimmer runs at 120 Hz to match the display. Two modes are offered: global dimming darkens the whole view, and segmented dimming lets applications darken only the part of the display behind virtual content, which Magic Leap says makes it possible to render black. The overall optical transmission of the headset is about 22%, and the white paper gives a maximum dimming contrast ratio of about 100:1. Road to VR, reporting on Magic Leap's January 2022 SPIE presentation, gave the adjustable transmission range as 22% to 0.3%. Before launch, the display analyst Karl Guttag read Magic Leap's patent applications as describing a polarization-based liquid crystal structure, and argued that each dimming pixel would be far larger than the display pixels, which limits how precisely this form of soft-edge occlusion can work.

Applications in AR glasses

In consumer products, electrochromic dimming is used in display glasses that show a large virtual screen. XREAL's own product comparison lists "3 Modes Electrochromic Dimming" for the XREAL One, One Pro and Air 2 Pro, all of which use Sony micro-OLED panels; the One uses birdbath optics and the One Pro what XREAL calls "X Prism" optics. Reviewers treat it as the alternative to the clip-on shades supplied with cheaper glasses.

Product	Maker	Electrochromic dimming as described by the source
Viture One	Viture	Electrochromic film; one press of the mode button switches the lenses between dark and light
Xreal Air 2 Pro	XREAL	Three levels, listed by XREAL as 0%, 35% and 100%; the only difference from the standard Air 2
Xreal One	XREAL	"3 Modes Electrochromic Dimming"
Xreal One Pro	XREAL	Three levels
Xreal 1S	XREAL	Darkness adjusted with a rocker switch on the temple
Viture Beast	Viture	Nine levels of tint

When TechRadar reviewed the Xreal Air 2 Pro in October 2023, it was available to pre-order at US$449 (the standard Air 2 was US$399), with shipping to US and UK customers expected in November. In TechRadar's review, Hamish Hector wrote that the electrochromic layer lets the lenses "swap between clear and shaded at the literal push of a button", with a fully transparent setting, a blacked-out immersive setting in which the real world is "(almost) entirely blocked out", and a setting halfway between; he said he still preferred the included clip-on cover when he wanted full immersion. Later research used the product as a benchmark: Wang and colleagues attached their own dimmer to a pair of Air 2 Pro glasses and compared its tint levels with the glasses' three built-in electrochromic levels.

Reviewing the Xreal One Pro in June 2025, Tom's Hardware's Brandon Hill wrote that the darkest of its three levels "doesn't completely block out all environmental light" but was enough for immersive video, and that with dimming at maximum little light came through even when he faced a sunlit window. He called electrochromic dimming "the more expensive option" but "highly preferable for AR glasses", comparing it with the clip-on black plastic shields used on cheaper models.

Viture has used electrochromic lenses since the Viture One, which Gaming Nexus reviewed in November 2023. The reviewer found the darkened lenses less effective on sunny days but used them more often than clip-on shades. For the Viture Beast, reviewed in April 2026, Tom's Guide counted nine levels of electrochromic tint and a feature that adjusts the tint as the wearer moves their head. Gaming Nexus, reviewing the same model, reported that the Beast's dimming showed visible bands rather than the uniform darkening of Viture's earlier glasses, which made it less effective in sunlight than the Viture Pro XR or the Xreal One Pro.

Research

A central research goal for electrochromic dimmers is a higher transmittance contrast, which requires both a darker tinted state and a clearer bleached state. The 2018 Sony device was built on a bendable plastic substrate. In 2025 Wang and colleagues reported a zinc anode and tungsten oxide (Zn-WO₃) dimmer with a photochromic hydrogel electrolyte, so that the device responds both to voltage and to light. With the two effects combined, it reached a transmittance contrast of 83.1% at 633 nm and a tinted transmittance below 1.5%, with 85.3% transmittance in the bleached state; a 5 by 5 cm device colored in 8.1 seconds and bleached in 5.8 seconds. Attached to Xreal Air 2 Pro glasses, the dimmer gave four dimming levels, and its darkest combined state was significantly darker than the glasses' own darkest mode.

See also

• Optical see-through
• Video see-through
• Occlusion
• Optical combiner
• AR glasses