Lidar is a key technology being used in the development of autonomous vehicles. But there are concerns about the potential effects of the lasers it uses on cameras and the human eye.
Lidar, a sort-of acronym for “light detection and ranging,” uses laser beams to sweep across the environment and deduce objects and their distance and speed. Developers of autonomous trucks are using lidar, along with cameras and radar, to allow the vehicles to “see” the world around them.
Automotive lidars fire laser pulses in the near-infrared spectrum to produce a cloud-point representation of the vehicle’s surroundings. The lidar unit measures the time elapsed between the pulse and when the pulse returns to the unit to measure the distance to an object.
However, the lidars used to guide autonomous light-duty vehicles, such as passenger cars, emit light energy with a wavelength of 905 nanometers, which is known to cause eye damage at certain intensities. To prevent eye damage, the U.S. and other countries restrict the 905-nm lidar’s power output, which limits its effective range to about 200-300 feet.
While that distance may be suitable for a car operating at 20-30 mph, it’s not good enough at highway speeds, where ranges of 600-1,000 feet are needed to identify hazards and provide a safe stopping distance. To overcome that limitation, some lidar companies have turned to a 1,550-nm laser that’s said to be 40 times more powerful with a range of up to 1,000 feet. And they’re safer for eyes, as well.
“If lidars use 1,550-nm lasers, the ocular fluid inside the eyeball prevents the laser light from reaching the retina at the back of the eye, which is by far the most sensitive part of the eye,” says Jeff Hecht, a contributing editor at Laser Focus World who has written numerous articles on lasers and vision safety. “The ocular fluid is largely clear at visible wavelengths and out to about 1,300 or 1,400 nm but becomes nearly opaque (think welder’s glass) at 1,550 nm.”
A high-power laser emitting 1,550 nanometers could burn the cornea at the front of the eye, but it would not reach the retina, Hecht says. “On the other hand, 905-nm light does reach the retina and could cause eye damage. I wouldn’t want one of those in my car or truck.”
There is also a question about whether the 1,550-nm lasers used in some truck lidar systems can damage some types of camera sensors, particularly those used by robotic vehicles to visualize the world around them.
An incident occurred at the CES electronics show in 2019 in Las Vegas where a camera sensor was reportedly damaged by a 1,550-nm lidar unit, but it was never proven conclusively.
“Camera sensors in general are known to be more susceptible to damage than the human eye,” warns the International Laser Display Association. The group explains on its website that the “extent of damage can vary widely, depending on distance from the source, beam direction and power.”
Several factors could impact a lidar’s effect on nearby cameras, such as the intensity and duration of the pulse. Shorter pulses can measure distance more accurately, but they require higher power intensity, and that can affect camera sensors.
None of this has yet been proven conclusively, but it could have implications for the reliability of camera-based perception systems on autonomous vehicles.