TOF VL53L1 autonomous mode with ambient light

[abdmou]

Hello,

We are using the VL53L1 sensor in autonomous mode to range data, mostly indoors but sometimes outdoor.

Following the Table 3 in UM2133, we use the short distance mode in order to have better ambient light immunity when outdoors.

However, in the AN5573, Table 6, it says that the outdoor capability in autonomous mode drops to a max distance of 200mm, but our targets are often in the 60cm-100cm range.

Is the sensor not usable in autonomous mode at all for our application outside ?

Please share any insights, experiences or recommendations regarding the VL53L1's autonomous mode ranging performance in outdoor/ambient light scenarios.

[John E KVAM]

How well the sensor works outdoors depends on quite a number of environmental factors.

To be honest, it doesn't work very well in sunlight. 

But how well is difficult to say. 

Sunlight hitting the target from behind the sensor is the worst case as photons from the sun are reflecting back to the sensor. 

Sunlight perpendicular to the line between the sensor and the target is best case as the sunlight tends to just pass through. 

How bright the day is matters too. 

940nm light from the sun will saturate the sensors photon detector and you end up with no headroom to detect the signal from the sensor.

I always recommend you test it in your expected environment. sometimes just turning the sensor 90 degrees will help, or sometimes your structure can shade the sensor somewhat. 

In short-distance mode, there are more pings per millisecond, so you end up with a stronger signal. This can help a little, but there is not much that can be done in strong sunlight.

- john 

[abdmou]

I understand that it is harder to measure in the sunlight.

My main inquiry is to differentiate between the autonomous mode preset and the ranging mode preset, according to the application note, the latter have a better range (1600 mm for a high reflectance target).

I tested the worst configuration you mentionned and I can measure up to roughly 25cm before getting ranging statuses 1 and 2 (for sigma and signal), which corresponds to the performances announced. Can the ranging preset mode do better ? Or will it be limited due to sunlight as well ? 

You said "sometimes your structure can shade the sensor somewhat.", don't we need both target and sensor shaded ? In my tests, having the sensor shaded didnt affect the outcome much.

Thanks again for your time.