A Clearer View: How IR Pass Filters Power Flawless VR & AR Tracking

A Clearer View: How IR Pass Filters Power Flawless VR & AR Tracking

Modern VR and AR headsets perform a clever trick. While your eyes see a vibrant digital world, the headset’s cameras are seeing something else entirely: a world illuminated by invisible, near-infrared (NIR) light. This allows the device to track your hands, controllers, and eyes with incredible precision, no matter what’s on the display.

The unsung hero behind this magic is the IR pass filter. This small but mighty component is designed to do one job perfectly: let the essential NIR tracking light reach the camera while blocking out all the distracting visible light from the display and your surroundings.

At KUPO Optics, we specialize in creating these critical filters. This guide breaks down how they work, what to look for, and how we can help you integrate them seamlessly.

Why Do IR Pass Filters Make Such a Big Difference?

An IR pass filter essentially gives your headset’s tracking cameras a clean, high-contrast view to work with. The result is a more stable and reliable experience for the user.

• Cleaner Tracking: The camera focuses only on the NIR light from the headset's own emitters (LEDs or VCSELs), ignoring confusing signals from room lights or reflections.
• No More Digital Noise: By blocking light from the bright internal displays, the filter prevents "crosstalk" that can confuse the tracking sensors.
• Consistent Performance: Whether the user is in a dark room or a bright office, the tracking remains stable and predictable.
• Better Power Efficiency: With a stronger signal, the headset's NIR emitters don't have to work as hard, which can help extend battery life.

Core Applications in Every Headset

You'll find IR pass filters at the heart of every modern XR tracking system:

• Hand and Controller Tracking: Outward-facing cameras use filters to lock onto your hands and controllers, which are lit up by the headset’s NIR sources. This prevents interference from sunlight or shiny objects in the room.
• Eye Tracking: Inward-facing cameras monitor your pupils by tracking reflections from low-power NIR emitters. A good filter ensures that your iris color, makeup, or even the display’s flicker don’t throw off the gaze estimation.
• Depth Sensing: Advanced systems like structured light or Time-of-Flight (ToF) need an extremely clean signal. A filter with a tight passband, precisely matched to the emitter, is crucial for accurate 3D mapping.
• Environment Mapping (SLAM): To map a room for positional tracking, cameras need to see clear features. A filter enhances the contrast of surfaces under NIR light, making the mapping process faster and more robust.

The Big Choice: 850 nm vs. 940 nm Wavelengths

Most XR tracking systems are built around one of two near-infrared "colors" or wavelengths. The choice depends on balancing performance with user comfort.

The 850 nm Band This is the workhorse for many systems.

• Pros: Camera sensors are typically very sensitive to this wavelength, resulting in a strong, clean signal. The ecosystem of emitters and sensors is well-established.
• Cons: Emitters at this wavelength can produce a very faint red glow that might be visible to users in dark rooms. It can also be more susceptible to interference from direct sunlight.

The 940 nm Band This wavelength is prized for its stealth.

• Pros: Emitters are completely invisible to the human eye, making it perfect for user-facing applications like eye tracking where you want zero distractions.
• Cons: Camera sensors are often less sensitive at 940 nm, so the system design needs to account for this to maintain a strong signal.

Many devices use a hybrid approach, such as 940 nm for eye tracking and 850 nm for world-facing cameras. Not sure where to start? Check out our 850 nm & 940 nm options for inspiration.

Key Design Tips for Optimal Performance

Specifying a filter involves more than just picking a wavelength. Here are a few key considerations:

• Passband Width (FWHM): This determines how narrow or wide the "gate" is for letting light through. A typical 30–60 nm width offers a good balance of signal strength and noise rejection. For systems in very bright environments, a narrower 10–30 nm band can provide extra immunity.
• Blocking Power (OD): You need to block all the visible light you don't want. This is measured in Optical Density (OD), where a higher number means stronger blocking. A target of OD 2 to OD 4 (blocking 99% to 99.99% of light) is a great starting point for the 400–780 nm visible spectrum.
• Angle of Incidence (AOI): Light from a wide-angle lens doesn't hit the filter straight-on; it comes in at an angle. This can shift the filter's performance. A good rule of thumb is a 1–2 nm shift for every degree of angle. We design our filters to perform correctly at your specific use-angle, not just in a lab test.
• Anti-Reflection (AR) Coatings: To maximize light throughput and prevent distracting ghost images, high-quality AR coatings on both sides of the filter are essential.

Materials and Durability Matter

An XR headset is a consumer device that has to withstand daily life. We build our filters to last.

• Substrates: We use robust optical materials like B270 and aluminosilicate glass that balance performance and durability.
• Thickness: Typical filters are between 0.5 mm and 2.0 mm thick, balancing weight with rigidity.
• Durability: Our hard-coated AR stacks resist scratches from routine cleaning and are tested to perform reliably from −20 °C to +70 °C (−4 °F to 158 °F).
• Stray Light Control: Features like blackened edges help minimize internal reflections, ensuring the camera sees only what it’s supposed to.

How We Ensure Quality

Confidence comes from data. We use calibrated spectrophotometers to verify every aspect of filter performance—peak transmission, center wavelength, and blocking power—at the angles relevant to your device. We provide clear, actionable data that connects directly to your camera's real-world performance.

Why Partner with KUPO Optics?

We support headset development teams from the first sketch to high-volume production.

• Expert Design: We create custom passbands tuned specifically for your lens, sensor, and use-case.
• Custom Shapes & Sizes: We deliver die-cut, diced, and uniquely shaped filters designed to fit into even the tightest device bezels.
• Rapid Prototyping: Get functional samples quickly to validate your design and accelerate development.
• End-to-End Support: We provide more than just a part; we offer design modeling, manufacturing guidance, and comprehensive measurement data.

Summary

IR pass filters are the quiet enablers of the immersive tracking that makes modern VR and AR possible. By choosing the right wavelength, planning for real-world angles, and specifying durable, high-performance coatings, you can ensure your device performs reliably every time.

KUPO Optics delivers the AOI-tuned designs, custom geometries, and expert support needed to get from prototype to production with confidence.

Ready to start validating? [Request a sample or custom size today.]