How the VL53L1X compute the distance if 2 or more target in the FOV , but in different distance?

[slian.4]

for VL53L1X sensor, if one target (distance is 1 meter) is partial in the FOV, and another target ( distance is 2 meters) is also in the FOV, so how the sensor calculate the distance, will it average the distance based on lights it got from different target? or it can detect only the nearest target distance? 

another question is: we tested the eval board, we put the target within the FOV, but not cover whole FOV and not in the center emission line ( 0 degree direction), it can not be detected. only when the target is close to the center emission line, it can be detected. we tried different kinds of target, no one can be fully detected. so the FOV is really 27 degree, or smaller than that? ( we set to short range, middle range, long range, but no help) 

[John E KVAM]

The simple answer is that the VL53 averages all the photons it sees.

But the reality of what happens is not so simple.

Take two objects - say at 1m and 2m, each covering half the Field of View (FOV).

One might expect an answer of 1.5m - but that would be wrong

The return signal decreases as a square of the distance. So the answer will be much closer to 1m - something like 1.2m.

But the size and the reflectivity of the objects come into play as well. A bright, near object might dominate the 'average', or if the near object were dull and the far object were very reflective, the result will be skewed toward the far object.

But if you look at the 'Sigma' result which is given in millimeters you will see that the result for one object is very small, and it will be much larger for the 2 object case. That will give you some hint about the result.

Finding a object near the edge of the Field of View is tricky. The sensor needs a minimum number of photons to get a range. (0.5 Mega counts is the default setting.)

You can lower that number - you will get an answer, but it will be less accurate.

And different objects have different reflectivities. Cotton is not particularly reflective at 940nm, whereas wool is VERY reflective. And interestingly, the color does not matter at all.

Best thing you can do is keep testing with the EVK, But beware - we only plot those points that return a 0 status, but the range can be valid with other warning statuses. Log the data and examine it, You will see far more ranges that are valid but have warning statuses.

[slian.4]

ok, clear . thanks