Infrared

Infrared (IR) radiation is electromagnetic radiation with wavelengths longer than those of visible light. The international standard ISO 20473:2007 places visible radiation between 380 nm and 780 nm and defines infrared as the band from 780 nm up to 1 mm, divided into near infrared (780 nm to 3,000 nm), mid infrared (3,000 nm to 50,000 nm) and far infrared (50,000 nm to 1 mm). Near-infrared light is invisible to the human eye, so it can illuminate a user's eyes without distracting them, and it is used throughout virtual reality and augmented reality hardware: in marker-based controller and headset tracking, in laser-sweep base stations, in eye tracking and face tracking cameras, in camera-based hand tracking, and in depth sensors.

Reviewed 27 September 2026. Checked the ISO 20473 band limits, NASA history and wavelength facts, and every tracking, eye, face, hand, depth-sensing and eye-safety claim against its cited source. About review dates.

Definition

ISO 20473 divides optical radiation into named spectral bands for optics and photonics. It restricts the word "light" to visible radiation (380 nm to 780 nm) and says the term should not be used for radiation outside that range. In its table, near infrared (NIR) covers 780 nm to 1,400 nm (the IR-A band) and 1,400 nm to 3,000 nm (IR-B); mid infrared (MIR) covers 3,000 nm to 50,000 nm and far infrared (FIR) covers 50,000 nm to 10⁶ nm, with IR-C spanning both. Other fields use their own divisions: NASA notes that Earth scientists call the region from 8 to 15 micrometres "thermal infrared", because those wavelengths are best for studying heat radiated by the planet.

The XR devices described in this article work in the near-infrared part of the spectrum. A typical television remote control uses infrared at a wavelength of around 940 nm. The Leap Motion Controller tracks light at 850 nm, and a 2026 research eye tracker for VR headsets used 850 nm LEDs because that wavelength is outside human visual perception and has been used widely in earlier eye-tracking systems.

History

William Herschel discovered infrared in 1800. While measuring the temperature of the different colors of the visible spectrum, he found that the readings rose from blue to red, and that a thermometer placed just beyond the red end of the spectrum recorded an even higher temperature.

Infrared camera tracking also appeared in consumer game hardware before the current generation of VR headsets. Johnny Chung Lee published projects built on the Nintendo Wii Remote, which, he noted, contains a 1024x768 infrared camera with built-in hardware blob tracking of up to four points at 100 Hz. In his "Head Tracking for Desktop VR Displays" project the Wii Remote's camera tracked a head-mounted sensor bar made of two IR LEDs, and the software rendered view-dependent images so that the screen behaved like a window into a virtual scene.

Oculus VR added IR marker tracking to its development kits with the Oculus Rift DK2, announced in March 2014. The headset's IR LEDs sat behind an IR-transparent housing (the earlier Crystal Cove prototype had visible white dots) and was tracked by a custom camera made by Oculus.

Applications in VR and AR

Active LED marker tracking

In the Constellation system used by the original Oculus Rift, each tracked device carries a predefined pattern of IR LEDs hidden under its outer plastic. External sensors, which are cameras with filters that pass only infrared light, send frames to the PC over USB at 60 Hz, and the PC locates each LED in the image to work out the position of the headset and controllers. Each LED also blinks at its own frequency to identify itself. Developers who reverse engineered the DK2 in 2014 found the same scheme: each LED flashes in a specific pattern at varying brightness, which lets the camera tell the lights apart. In a 2019 Oculus developer blog post, Andrew Melim described the next step, working out which specific LED produced each bright blob in the camera image, as the "LED matching" problem.

Standalone headsets moved the cameras onto the headset while keeping IR LEDs on the controllers. In Facebook's description of Oculus Insight, infrared LEDs in the controllers are detected by the headset cameras, which lets the system limit the position drift that builds up when readings from the controllers' inertial sensors are integrated. The Meta Quest Touch Plus Controllers for the Meta Quest 3 dropped the tracking ring; Meta CTO Andrew Bosworth said they still carry infrared LEDs, placed on the controller face, and Meta fuses that LED tracking with the headset's controller-free hand tracking and the controllers' accelerometers and gyroscopes. The specifications Sony gave for the PlayStation VR2 likewise list four external IR cameras and inside-out tracking with no external beacons.

Laser sweep tracking

Valve's Lighthouse system reverses the arrangement: instead of cameras watching LEDs, base stations light up the room and sensors on the tracked objects measure timing. Each base station emits a bright IR flash and then sweeps a wide IR laser beam across the room, one axis at a time. Headsets and controllers carry arrays of IR photodiodes connected to a chip that measures, for each axis, the time between the flash and the moment the laser sweep strikes each sensor. Hackaday noted in May 2015 that this approach needs only a dozen or so inexpensive photodiodes on the headset and lets the angle to the base station be computed in a few microcontroller cycles. Not every tracked VR system uses infrared: the original PlayStation VR tracked visible light from blue strips on the headset and glowing orbs on its controllers.

Eye tracking

Camera-based eye trackers such as Tobii's illuminate the eyes with near-infrared light and image them with cameras. Tobii describes the method it uses, pupil center corneal reflection (PCCR), in which the pupil center and the reflection of the light source on the cornea are detected in the camera image to calculate the gaze point; the company says near-infrared is used because it is invisible to the eye, so it causes no distraction, and gives stable illumination. Elias Guestrin and Moshe Eizenman published a general theory for estimating the point of gaze from the centers of the pupil and the corneal reflections in 2006, covering the full range of possible system configurations.

Inside a headset the illuminators are usually arranged around the lens. The 2026 system by Lv and colleagues placed eight near-infrared LEDs in a ring around the inner edge of the headset lens and captured the eye with a near-infrared camera. Commercial examples include:

• PlayStation VR2: two internal IR cameras for eye tracking.
• Microsoft HoloLens 2: two infrared cameras for eye tracking.
• Apple Vision Pro: Apple describes an eye-tracking system of high-speed cameras and a ring of LEDs that project invisible light patterns onto the user's eyes, and says its Optic ID authentication analyzes the iris under various invisible LED light exposures.

Face tracking

The same approach extends to the lower face. Meta Quest Pro uses five inward-facing infrared sensors for eye and face tracking: three aimed at the eyes and upper face and two at the lower face. The HTC Vive Facial Tracker accessory, announced in March 2021, pairs two cameras running at 60 Hz with an IR illuminator that keeps the area around the user's mouth lit, and tracks 38 facial movements across the lips, jaw, teeth, tongue, chin and cheeks.

Hand tracking and low-light illumination

The Leap Motion Controller is built around two cameras and three infrared LEDs. Because it tracks in the near infrared, its camera images are grayscale, and the company noted that strong sources or reflectors of infrared light can make hands and fingers harder to distinguish. Some headsets add IR floodlights to light the hands for their own tracking cameras. The Meta Quest 3S has two IR illuminators beside its front cameras; they help the IR-sensitive tracking cameras get a bright view of the user's hands and nearby objects, which UploadVR found gave it better hand tracking in low light than the Quest 3. The Quest 3 has no such illuminators; its central infrared depth projector appeared in UploadVR's testing to be used only during mixed reality scene mesh scanning. The same report noted that Apple Vision Pro also has two IR illuminators on the front.

Depth sensing

Active depth sensors often project their own infrared light. Pagliari and Pinto's comparison of the two generations of Microsoft Kinect says the first measures distance with a coded light technique: an IR projector casts a speckle pattern onto the scene and an IR camera captures the reflected pattern to compute depth for each pixel. Microsoft defines the second, the Kinect for Xbox One, as a time-of-flight system; the authors point out that the quantity it actually observes is the phase shift of a modulated signal, from which depth is computed. Microsoft said in 2013 that the new sensor's infrared capability would let it recognize people and track bodies with little or no visible light.

Eye safety

Because infrared illuminators in headsets and trackers shine toward the eye, their output is assessed for photobiological safety. An application brief from LED maker Lumileds explains that IEC 62471:2006, "Photobiological safety of lamps and lamp systems", sets exposure limits for the eye and skin that depend on exposure duration and on whether a source emits continuously or in pulses, and sorts lamps and LEDs into risk groups that can require warning labels and user instructions. For near-infrared sources the relevant limits cover thermal effects on the cornea and on the retina, where the eye's lens focuses an image of the source.

See also

• Tracking
• Outside-in tracking
• Inside-out tracking
• Positional tracking
• Structured light
• Ultraleap