Lidar, Optical Distance and Time of Flight Sensors
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LidarTime-of-Flight SensorsAutonomous Vehicles3d Sensing
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Lidar
Time-of-Flight Sensors
Autonomous Vehicles
3d Sensing
The article discusses LIDAR and time-of-flight sensors, sparking a discussion on their applications, advancements, and challenges in the field of autonomous vehicles and 3D sensing.
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The trend in China and Japan is a long-range forward-facing LIDAR coupled with three shorter-range units for side and rear coverage.[1] The long-range unit still costs around US$10,000. This should come down with volume.
[1] https://www.robosense.ai/en/news-show-1908
[2] https://openelab.io/products/robosense-em4-thousand-beam-lon...
But from an optical and electronics point of view, it's much harder to process the return signal that way, and probably uses a lot more energy due to the processing required (with current tech).
The reason is that you can time-gate the noise out that would otherwise be hitting your correlation accumulators if you have a vague idea of the supposed delay/ToF for the pulse.
However, once you add mechanical scanning, at least for systems with not that many orders of magnitude between range resolution and maximum detection range, you can use systems like mode-locked lasers that for example have around 0.1% native duty cycle, circumvent the issue of peak power through the aperture/scanning 's spatial focusing (each pixel only needs a managable amount of energy, and delivering that in a single pulse won't require unreasonable peak power levels), and still get all the energy-efficiency benefits of single-pulse ranging vs. spread-spectrum/correlation ranging.
The only but major downside is the requirement of mechanical scanning.
That's where the beam diameter at the target is much larger than the target, as for aircraft. With a small scanning dot from a LIDAR and a nice big target like a car, almost all the power hits the target, but you still have inverse square losses coming back.
Second part of the comment I omitted is was what You mentioned in the beginning. Those 20-30 meters of practical range is why we keep seeing small LIDAR sensors on things like iPhones / iPads (though there I believe the range is even a bit shorter due to the size / power constraints), but not really much beyond that.
For practical demo of what's currently available at the high end of solid state LIDAR (albeit at 40k+ USD), I'd suggest looking at Leica and their BLK2GO PULSE (solid state) vs the rest of the BLK line (rotating laser spot).
For how long? Can't be continuous. What's average power. Yes, flash LIDAR has a power problem. How does their long-range LIDAR work?
> Another influence certainly is that the automated driving craze has been superseded by the AI craze and scaling won't come in the time frame that was predicted some years ago.
Huh. Good point. Want to think about that one.
We might max out at most taxis being self-driving, because that works and sells, but not make it to personal vehicles.
> P.S.: a QNX desktop is possible and actually alive again, but company politics... :/
I'm out of that now. The closed source/open souce/closed source/open source/closed source transitions angered too many people. There was once Netscape/Firefox for QNX.
However, the chances anyone will see that technology in a consumer product is very low. These were also never cost effective, and priced several times more than most cars. Additionally, like all optics these couldn't handle excessive dust, rain, direct sunlight, and bug guts.
Most platforms included millimeter Radar for when vision and LIDAR/LADAR optics fail. QNX simply missed its largest market launch window in the 1990s, and is no longer the path forward for a lot of projects. Note "AI" might be real someday (unlikely an LLM), but every hype-cycle needs to run its course. =3
two seconds of googling: https://www.digikey.com/en/maker/tutorials/2021/understandin...
This guy gets close:
https://www.youtube.com/watch?v=MUdro-6u2Zg&t=770s
But why isn't something cheap and small like this commercially available as an integrated system?
Last I looked CD readers used a 4-detector sensor's differential low-pass signals for closed-loop track-following so the rotation need not be optically centered. I also see no reason why optical disc readouts would need homodyne let alone heterodyne readout.
> Interferometry is a technique which uses the interference of superimposed waves to extract information.
And a blu ray player directly uses interference of superimposed waves to extract information. It squarely fits in the homodyne category.