That's operating temp without external heater. Storage temp is lower.
Even automotive cameras have built in heaters to allow them to operate lower than -20C. Nothing preventing adding the same functionality to our sensors.
This is the spec for a cold start. If you give it a warm start, you can operate it much lower than -20C! For instance, it's being used in underground mines in Scandinavia without issue.
The issue will not be at cold but at high temperature. VCSELs have very poor efficiency at high temperature and it’s possible to operate them where increasing current reduces light output. In a vehicle application the temperatures are very high and humidity can also be very high and condensing.
This couldn't be further from the truth. You can design the VCSEL cavity and top and bottom mirrors for peak efficiency at any temp, including very high temps. I wonder what we did...
Compared to the side emitter diode lasers used in legacy spinning lidar, VCSELS are cheaper, more efficient, more reliable, longer life, and better quality light sources to boot.
Unfortunately the gain falls as function of temperature so you also get a lot less light and you have to pump harder (more current). So while it’s possible to somewhat compensate somewhat with the mirrors the device still has this behavior at high temperatures as the device self heats. This behavior is widely documented in the literature.
VCSELs have a smaller current aperture and the current density is higher than in an edge emitting laser. As the reliability is a function of the junction temperature and the current density, VCSELs operating at high temperatures have significantly reduced lifetime compared to an edge emitting device due to the high current density.
See for example slide 5 which shows how lifetime scales as a function of temperature and current density. For high reliability your devices need to have low current density.
We had some of problem trying Robosense lidars at very cold temperature. Didn't try our Ouster in such conditions to my knowledge. BUT most of the we got good results in temperature much colder than what the lidars were rated for. For the more sensitive lidars my lab developed a hacky warming apparatus using hand warmers :D
TL;DR: the operating temperature range of these sensors is small, nowhere near automotive spec, and a real problem at high temperatures. Also, watch the fine print on Ouster's thermal specs.
The bigger issue is hot weather; electronics and lasers work well (often more efficiently) at cold temps, and the electrical power running through them self-heats the components. The problem arises when the environment is already hot, and the components still self-heat. This is a particularly large problem for LiDAR, where lasers are very sensitive to temperature and typically use some sort of thermoelectric controller to keep the laser itself at a precise constant temperature. But these thermoelectric devices are inefficient at cooling and lose control (go into thermal runaway) when things get too hot.
Automotive component thermal specs (AEC-Q100) require operation (and start-up) at -40C up to anywhere from 70-150C depending on grade. Ouster's -10/-20C to 50C range actually relies on an external base heatsink being used, which they never picture and makes the sensor significantly heavier and larger. These sensors are a far cry from being ready for automotive use.
We didn't claim these were auto rated parts... that being said, our temp spec is in line with the industry, and we're dead set* on reaching auto temp spec in a future iteration of the product.
Our shock, vibe and ingress specs are far better than the competition and pass most auto specs already though. Ruggedness like this was unheard of in spinning lidar even two years ago.
*I believe our internal thermal design group is "cultofthelavapeople at ouster dot io".
