Man Says CES Lidar's Laser Was So Powerful It Wrecked His Camera (arstechnica.com)

An anonymous reader quotes a report from Ars Technica: A man attending this week's CES show in Las Vegas says that a lidar sensor from startup AEye has permanently damaged the sensor on his $1,998 Sony camera. Earlier this week, roboticist and entrepreneur Jit Ray Chowdhury snapped photos of a car at CES with AEye's lidar units on top. He discovered that every subsequent picture he took was marred by two bright purple spots, with horizontal and vertical lines emanating from them. "I noticed that all my pictures were having that spot," he told Ars by phone on Thursday evening. "I covered up the camera with the lens cap and the spots are there -- it's burned into the sensor." In an email to Ars Technica, AEye CEO Luis Dussan confirmed that AEye's lidars can cause damage to camera sensors -- though he stressed that they pose no danger to human eyes. "Cameras are up to 1000x more sensitive to lasers than eyeballs," Dussan wrote. "Occasionally, this can cause thermal damage to a camera's focal plane array." Chowdhury says that AEye has offered to buy him a new camera. The potential issue is that self-driving cars also rely on conventional cameras. "So if those lidars are not camera-safe, it won't just create a headache for people snapping pictures with handheld camera," reports Ars. "Lidar sensors could also damage the cameras on other self-driving cars."

"It's worth noting that companies like Alphabet's Waymo and GM's Cruise have been testing dozens of vehicles with lidar on public streets for more than a year," adds Ars. "People have taken many pictures of these cars, and as far as we know none of them have suffered camera damage. So most lidars being tested in public today do not seem to pose a significant risk to cameras."

Comments

1550 nm wavelength is (relatively) eye-safe

[Vadim Makarov]

As the original article duly explains, the laser light at the wavelength of 1550 nm used by this lidar scanner does NOT reach the retina of the eye. At this wavelength, it is fully absorbed in outer parts of the eye (cornea, lens, etc.) before it could get focused into a tight spot on the retina. This makes this wavelength (relatively) eye-safe, comparing to visible and some other wavelength ranges. There is no such protection for the camera however, whose glass optics happily focuses 1550 nm into a small spot... so the sensor damage may happen.

Laser safety regulations are primarily concerned with (a) no damage to humans, especially their eyes, and (b) laser beams not setting things on fire. Neither of this has happened in this incident. So we are good.

If you are interested in technical details of laser safety, read ANSI Z136.1 standard. Warning: it requires technical expertise.

Re:1550 nm wavelength is (relatively) eye-safe

[Vadim Makarov]

Maximum permitted exposure (MPE) in 1500-1800 nm band is the same for the eye and the skin. For continuous-wave light it is 0.1 W/cm2, for pulsed light it is 1 J/cm2. Reference: ANSI Z136.1, see Tables 5a and 7.

In other words, if the 1550 nm laser beam is not burning your skin, it is safe for your eye.

This is remarkably untrue at other wavelengths, where light is dramatically more dangerous to the eye than it is to the skin.

Re:Not just cameras

[Solandri]

Radar and sonar overcome this problem by constantly varying the frequency in a series of chirps. It's highly unlikely that there's another radar/sonar transmitting at the same frequency at near the same time. And even if there is, it's unlikely to be varying the frequency at the same rate/range.

Another advantage of this is that you don't need as strong a sweep signal. With a single frequency, you're emitting a pulse, then waiting for the reflections of the pulse. In order to avoid the possibility of spurious noise from another source being interpreted as a reflection, your pulse has to be high-power (basically make the reflected signal stronger in strength than any noise). 1000 to 5000 Watts was typical for boat radars using pulse beams. But when you use a varying frequency, you can compare reflections at one frequency with subsequent reflections at a different frequency (there's no need to wait for return reflections - subsequent pulses will not interfere with previous pulses, so can be sent before reflections from previous pulses arrive). Noise will show up at just one frequency, making it easy to spot and trivial to filter out. Consequently newer frequency sweeping boat radars only need to emit at a few tens of Watts.

That said, the parking sensors in your car use this frequency varying sonar. And I've noticed other cars' parking sensors trigger mine about once a day. So some more work needs to be done on standardizing frequency sweeps and noise filtering to reduce signal collisions. But the problem is not as insurmountable as you'd think from your LIDAR experience.