Could lidars damage camera sensors used on self-driving vehicles?
Evidence mounts that lidar systems installed on an autonomous vehicle may damage camera sensors installed on other autonomous vehicles
Can lidars damage sensitive camera chips?
The question has been asked many times following an incident earlier this month at the Consumer Electronics Show 2019 in Las Vegas, Nevada, when man complained that his digital camera had been damaged after taking a picture of a driverless car.
The man, Jit Ray Chowdhury, said he noticed purple spots on all his photographs after taking a picture of the driverless car that had a AEye's lidar laser scanning system on its roof.
The photographs showed horizontal and vertical lines emanating from the purple spots. Chowdhury, an autonomous vehicle engineer at the start-up Ridecell, was offered a replacement after complaining about the incident to AEye.
So, can lidars damage digital camera sensors?
Today, lidars have become an almost essential part of the self-driving cars, currently under development. Most experts believe such vehicles can't reach full autonomy without integrating lidar technology, and that we should be ready to see more and more lidar sensors installed on top of autonomous vehicles over the coming years.
At the same time, though, autonomous vehicles also rely on video cameras to locate and recognise objects in real time.
So, if lidars are not safe for digital cameras, they may also damage camera sensors installed on other self-driving vehicles.
Some companies use lasers of 905nm wavelength in their lidars. While those sensors can be easily made using standard silicon-based fabrication techniques, the lasers at these wavelengths can be harmful to the human retina.
So safety rules in the US put restrictions on the peak laser power. Lasers emitting invisible infrared light near 900nm should produce pulse of low powers, with measurement range up to 60 or 100 metres.
On the other hand, some lidars are made using lasers with a wavelength of 1550nm. Pulses from such lasers can reach ranges of 300 metres. These sensors are expensive to make, but are safe for human retina. AEye also uses 1550nm lasers, which can damage camera sensors, although they are safe for human eyes.
"Now is the time for people to look at this in depth," Dennis Killinger, a veteran lidar developer and professor emeritus at the University of South Florida, told IEEE.
According to Killinger, most lidar companies have not yet released detailed power specifications. Moreover, the duration of laser pulses are also important to consider. While most current automotive lidars use nanosecond pulses, concentrating the energy of picosecond and femtosecond pulses, while measuring distances, can increase the peak power of such pulses and could potentially damage a camera.
Killinger suggests this is the right time for lidar designers to start thinking about the safety and protection of autonomous vehicles' 'electronic eyes'.