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