How do the time-of-flight sensors (eg VL6180, VL53L0X ...) technically work in detail?

[Hanja_Frd]

I'd like to know how the tof sensors technically work in detail. I know about the principle (photons were sent and time taken until receiving the reflection), but how is the field of view created and how can some sensors have a lager FoV than others? What is the difference to a typical laser sensor?

[John E KVAM]

It all starts with the Vertical Cavity Surface Emitting Laser - VCSEL. The Field of View was simply a result of how they work. The Fiber optic market and the compact disk market for which they were built wanted a wide FoV. So it's a multi-stage VCSEL. A main beam lights up and very quickly after a outer ring lights up. ST adds a diffuser on top to smooth out the pattern of light. But the FoV is determined by the VCSEL physics.

(All the laser pointers in the world (and anything with a beam) use this same type of VCSEL, but they have a lens to focus the beam.)

The ST ToF sensors do NOT focus the beam. It's how we maintain our Class 1 optical safety.

The VL53L4 has a more narrow FoV because we use a single stage VCSEL that we designed.

The wider FoV of the VL53L5 and even wider VL53L7 is a result of a meticulously designed defusing optical element placed above the VCSEL emitter. These two sensors emit light in a prymid shape and not a cone. They are kind of amazing in that regard.

• john