That's a reasonable basic overview.
I'm surprised that rotating scanners are still used. It's been twenty years since Velodyne built their first one. They work OK, but cost too much. I was expecting flash LIDAR or MEMS mirrors to take over. Continental, the auto parts company, bought the leading flash LIDAR company over a decade ago, but the volume market a big parts company needs never appeared.
Waymo is still using rotating LIDARs even for the little ones at the vehicle corners. Those need less range. There needs to be a cheap, flush-mounted replacement for those things. The location is too vulnerable. Maybe millimeter phased array radar mounted behind Fiberglas body panels. Waymo needs to solve that problem before they do New York.
The LIDAR on top may not be a problem. Insisting that it has to go away to "look like a car" is like insisting that cars had to have the form factor of horse-propelled buggies. Early cars looked like buggies, but that didn't last.
One big advantage of pulsed LIDAR over continuous is that the interference problem between identical units is much less. The duty cycle is tiny. Data from one pulse round trip is collected in less than a microsecond. Just put some randomization in the pulse timing and getting multiple conflicts in a row goes away.
Waymo have in house radar, I think in the 70GHz gap in the absorption spectrum. They're pretty obvious as sort of paperback book sized planes, mounted near other sensors IIRC.
The old Velodyne units were actually susceptible to damage if you left two units running right next to each other. I did hear a proposal at some point for a different but similar unit to use GPS time to sync the rotations of all the units we had live so they wouldn't be pointed at each other, but in practice it seemed to not be a huge issue.
BTW I once gave you guff about continuing to bring up Conti's flash LIDAR, and in retrospect I wish I hadn't, I really enjoy your contributions here.
I went down to Advanced Scientific Concepts in Santa Monica, CA, in 2003 to see their prototype flash LIDAR. It was on an optical bench aimed out an overhead door into daylight, nowhere near a product. It did work, but required strange InGaAs semiconductor processes and a timer chip stacked back to back against the sensor chip. Way too expensive to fab.
I thought that was going to be the future, and that technology would get cheap. But it's still expensive to fab such devices.
Si interpoisers are a pretty mainstream packaging technology nowadays, so that might help with the stacking bits.
The SNR for flash Lidar is really low because you spread the beam out over such a large area.
Most automotive Lidar already operate in a “photon starved regime”, ~200-300 photons per return[0]. If you spread that over the entire scene, your snr drops quickly.
This forces you into 1550nm, and a large detector array and high power laser at 1550nm is extremely expensive.
As for MEMS, it’s been a while but I think FOV/steering angle range , steering speed and even maximum beam power were concerns
EDIT: my Lidar friend Jake reminded me that the appetizer size is also an issue with MEMS- smaller aperture = less light collected = lower SNR
[0] https://www.hamamatsu.com/content/dam/hamamatsu-photonics/si...
> Most automotive Lidar already operate in a “photon starved regime”, ~200-300 photons per return[0]. If you spread that over the entire scene, your snr drops quickly.
Translating: Normally you have a large single sensor per laser, which makes measurements at a very high rate. With flash lidar, you split the sensor up like an image sensor. In a normal image sensor, each pixel can collect light for a long time, but if you do that with lidar you have no distance resolution. The sensor is sitting idle 99% of the time, and you pay in sensitivity and accuracy.
Array sensors, MEMs, and phased arrays all struggle because they're all really good at small-angle differences, while the reason for scanning lidar is large-angle differences. Maybe one day we'll start making curved dies and it'll be easier to have a really wide FOV without needing multiple sensors.
You can actually make curved dies already- there’s a company doing that for image sensors, if you thin silicon down it becomes flexible
> I'm surprised that rotating scanners are still used. It's been twenty years since Velodyne built their first one.
They're even older than that. SICK have been pointing laser range finders into spinning mirrors since about 1995 - albeit mostly for industrial safety systems which can be quite price-insensitive.
There's a few things to know about LIDAR to understand why spinning lasers make sense.
First of all, anything emitting a cone of light encounters "inverse square dropoff" - where moving twice as far away means you get a quarter of the light, per unit area. This is most visible with flash photography at night - but it also applies to LIDARs. And in an automotive application, ideally you want to be able to sense things 100m away. Illuminating a laser spot is much more practical than illuminating everything.
Secondly, whatever light source you use has to be eye-safe. And sure, IR has safety advantages over visible light here - but a light source bright enough to illuminate things at a 100m distance would be very hard to make safe, even with the advantages of IR. As a scanning laser never lingers in one point for long, it can safely be much more intense.
The third thing to know is whatever light source you're using, you're in competition with the sun. Sometimes the sun is low in the sky and directly dazzling your sensors. Other times it's illuminating the same things you want to illuminate. This means you can't make up for a weak light source and inverse-square dropoff with clever signal processing.
And finally, the makers of these cars envisage a future where every single vehicle on the road is using this technology. So there's also a risk of the reflected returns of two different vehicles interfering with one another. Even rotating LIDAR can be vulnerable to it, but flash LIDAR is particularly vulnerable.
Meanwhile, automotive companies aren't scared of moving parts. A car has loads of spinning parts already; they have mastered the art of making spinning things that can keep spinning for thousands of hours.
> Meanwhile, automotive companies aren't scared of moving parts. A car has loads of spinning parts already; they have mastered the art of making spinning things that can keep spinning for thousands of hours.
Almost an understatement.
A typical car wheel hub with a 20-27 inch tire diameter has experienced around 75-100M full rotations by the time it reaches 100K miles.
Meanwhile, the engine probably has revolved ~5-10 times more during the same time.
I may be wrong, but I think the concern was delicate components protruding from the body are susceptible to damage in urban areas.
Cars already have mirrors and lights etc. LIDAR is in the same family as those.
I doubt MEMS will work on a moving vehicle. Luminar makes solid-state lidars that are used on EX90 Volvos. I suspect either their resolution or their FOV (120°) is not enough for proper self-driving.
> They work OK, but cost too much.
Costs have dropped dramatically in the past 20 years and continue to do so.
> There needs to be a cheap, flush-mounted replacement for those things.
Why? Corners are the optimal mounting position for maximum visibility. It allows the car to -in-effect- see around corners in ways no centrally mounted sensor can.
> Waymo needs to solve that problem before they do New York.
What? Because of vandalism?
Have you ever seen the corners of a car that has been parked in a big East-coast city? They will sustain damage during the course of normal operation and storage, and many people will not stop and leave their insurance information, especially if the damage is perceived as minor and happens while the car is parked and the owner not present. Currently, the corners of a car are relatively non-critical to its function and usually not too expensive to repair. If both of those change, we'll see more expensive damage that is more challenging to repair as well as less likely to be handled by the responsible party.
Also, having the sensors stick out from the corners makes the car's collision box and turning radius bigger. That doesn't help in any tight situation, but I imagine that's not that different between e.g. SF and New York. What is different is the sheer volume of cars and pedestrian activity.
Right. It seems to have been Waymo's decision to have zero blind spots around the vehicle perimeter, even if that means having the sensors stick out.
Cruise had an accident where another vehicle knocked a pedestrian into a Cruise car, and the pedestrian was dragged. Cruise lost their California DMV autonomous license for that. So there's a good case for full perimeter coverage.
Humans don't have that. The same week as the Cruise incident, a NYPD tow truck dragged a pedestrian some distance because they were in a blind spot for the driver.
They lost their license for not reporting it properly (as required under the license). Not for the accident.
> Cruise had an accident where another vehicle knocked a pedestrian into a Cruise car, and the pedestrian was dragged. Cruise lost their California DMV autonomous license for that
Cruise didn't lose the license because the car and/or human operator accidentally dragged a pedestrian (similar to the NYPD Truck). They lost their license because some time after the accident, Cruise employees fully aware of what transpired chose to cover up that part in their report of the accident to the state regulators. The state regulators found it out anyway.
They don't stick out that much. The geely vehicle has front sensors recessed just above the front wheel well, without much additional side clearance. Either way, a collision involves regulatory filings, downtime, and sensor recalibration even if no damage is sustained.
Waymos sometimes stop briefly in parking spots while waiting for assignments, but they don't really park as such except in special lots. The big problem I have seen is they tend not to always pull to the curb when releasing passengers and if a door is left even slightly ajar then they will sit there requesting the door be closed even if they are blocking a lane with many cars behind them beeping.
Not having a motor and thus having to depend on people to close doors on an autonomous car seems very silly.
Waymo's custom designed 6th generation vehicles[1] with self-closing doors were expected to enter service this year, but have [probably] been put on indefinite hold due to tariff issues
[1] https://waymo.com/blog/2021/12/expanding-our-waymo-one-fleet...
Minivans have had powered doors for decades and make great taxis, why do they need a special vehicle for this?
An earlier version of Waymo's vehicle was based on the Chrysler Pacifica. Like in a lot of areas, if you're going to spend billions of dollars to buy thousands of some product, it is worth customizing it for the specific purpose.
I think it’s due to how often cars bump or scratch against each other in NYC (I.e. the sensors are in a vulnerable spot to be easily damaged).
It’s quite funny seeing the number of cars that have bumper skirts in NYC to help minimize damage from inevitable close encounters with other vehicles