Attack of the 1,550 nm Wavelength

You know those fancy-shmancy new LiDAR gadgets that turn self-driving cars into futuristic robots? Apparently, they hate your camera. Or, at least, your camera sensor. And maybe your rods and cones, too.

LiDAR (Light Detection and Ranging) is a pretty rad piece of technology. LiDAR uses laser light to create a 3D model of an environment. It works by emitting laser pulses and measuring the time it takes for each pulse to bounce back after hitting an object. Basically, it shoots a laser pulse, waits for it to bounce back, and then times the round-trip. Easy peasy! Do this thousands of times per second and boom—you got yourself a detailed 3D map of wherever you are.

Apparently this awesome piece of technology—which might someday allow Charlotte drivers snooze while driving down I-277—has been around since the '60s and even powers space satellites. Unfortunately, it is camera's kryptonite. A Reddit user shared a video in a r/Volvo subreddit showing damage to his iPhone 16 Pro Max camera after filming the LiDAR sensor on a Volvo EX90. As the user is filming the sensor, you can see purple specks appear on the video.

This issue is not new at all. In 2019, a photographer had his Sony mirrorless camera ruined at CES after snapping a demo car with a powerful LiDAR sensor. The photographer also discovered these purple specks on his photos. In fact, Volvo and other manufacturers know this as evident by Volvo's warning to owners.

How LiDAR Lasers Can Destroy Camera Sensors

Remember, LiDAR works by firing rapid pulses of laser light to measure distance. Camera lenses will focus that laser energy onto the senor's pixels, kind of like staring into the sun. This intense energy LiDAR systems can emit overheats and literally burns the sensor's components.

There are several factors at play here: wavelength, power, focus, and exposure time. In the Volvo EX90's case, the LiDAR system uses a 1,550 nm near-IR laser which is much more powerful than LiDAR systems used in older cars which are sometimes 905 nm. This high-powered laser extends the range of the LiDAR pulses. And when you give a camera lens too long of exposure to the lasers, more and more heat gets dumped onto the camera's components.

Can LiDAR Damage Human Eyes?

Yes. Yes they can.

Do you remember the early days of autonomous vehicles? Think those ugly looking Waymo protoypes. Those used 905 nm LiDAR systems. Why 905 nm? Well, cheaper, used readily available silicon detectors, and worked well with those spinning rooftop turrets that made all those self-driving cars look like city ordinances.

905 nm unfortunately penetrates all the way to the human retina. The eye focuses this wavelength onto the retina like a magnifying glass on dry leaves. And the retina? Oh it doesn’t grow back.

Safety rules required limiting the emissions at the 905 nm wavelength, drastically dropping the range of the LiDAR system to close to 100m—which to put in perspective—the range is good enough to able to spot hazards and stop autonomous vehicles moving 20 to 30 mph. So definitely not for Charlotte interstate highway drivers.

In short: 905 nm LiDAR could damage your eyes if misused, so engineers had to throttle its power down. That trade-off—eye safety vs. range—is a big reason why modern systems are moving to 1,550 nm.

So hold on... If 905 nm wavelength LiDAR sensors are capable of hurting human retinas so much that they needed to reduce the range, why are the 1,550 nm LiDAR systems a thing now?

There are other parts of the human eye that absorb wavelengths longer than 1,400 nm. These parts of the human eye like the cornea (and other anterior parts of the eye) are affected by 1,550 nm. Visible light and near-IR light (approx. 400-1,400 nm) zoom right through the front of the eye and focus on the retina at the back. Infrared light beyond 1,400 nm is largely absorbed by the front parts of the eye. They absorb the wavelength due to the high water content in these tissues to the point that it does not even reach the retina.

Sounds scary right? I mean the cornea which is part of the anterior of the eye is kind of used to help focus light; why would we want that destroyed? Simply put, the anterior parts of the eye can withstand more energy. The retina is delicate, it is full of light-sensitive cells, and struggles to regenerate well. Anterior region is mostly made up of water and proteins that can absorb IR heat better.

Having said all of this, you're not entirely safe. 1,550 nm is not risk-free. If the intensity of the LiDAR system is high enough, your cornea or lens can be injured due to all of the energy from the laser being absorbed by those tissues. The resilience to damage is just much higher for the anterior tissues compared to your retina is all.

So How About Those Safety Standards?

The safety of laser products (yes this is a real thing) is governed internationally by the IEC 60825-1 standard. This standard defines laser classes based o ntheir potential to cause injury. Class 1 is the safest while Class 4 is the most dangerous. Class 1 lasers are considered “safe under reasonably foreseeable use, including the use of optical instruments for intrabeam viewing”.

For the automotive industry, the LiDAR systems are considered Class 1 laser products. Governments love rules, and they have got plenty here (fortunately). Bodies like the UNECE, ISO 17387, etc. all have regulations that require any laser-emitting part on a vehicle comply with the IEC laser safety requirement and verify that a LiDAR system carries a Class 1 certification before using it on their cars.

Conclusion

Phew. Look, there is honestly a ton more we could dive into—physics, biology, and even beauracracy. If you geek out on this stuff, check out the LiDAR Safety Standards and Exposure sheet by QuantumLABS. Your eyes are safe. Your cameras, not so much. Unless you're careful.